LR Cln F

FAQs about Live Rock Cleaning & Avoiding Unwanted Hitchhikers

Related Articles: Curing Live Rock by Bob Fenner, Live Rock, Reef Systems, Refugiums,

another "setting the tank back up" question. LR, rdg. 6/22/16
<Can't open your graphics>
first, thanks for the advice on resetting my substrate.

now, about my old LR.
<Have you searched, read Re on WWM?>
i was planning on bleaching it and using it as base rock. most of the “sunny sides” are covered in a tough mat of algae. i don’t think even a brass wire brush will totally remove it. (pic attached FWIW—the pic makes it look like the algae has some depth to it, but it is a tight coating and only 1/8 to 1/4 inch deep).
however, when i removed it, i found that several pieces have a good population of small tube worms and polyps. i hate to kill them.
<Then don't>
if i reuse the pieces with wildlife on them, invert them so most of the algae surfaces aren’t receiving much light (the former bottom surfaces have some coralline left on them), what risk am i running of the algae propagating to the new LR that i will be adding?
<Depends on the circumstances... IF they favor the algae, mix of Protists, Monerans. B>
thanks!
ken baker

Cooking live rock vs. new 4/27/15
I’ve decided to hit the reset button on my ten year old 30gallon reef tank.
<Aah!>
For the past few months it’s been running mostly unlit with just live rock/sand (no fish or inverts), due to several issues that I could never overcome despite my best efforts (algae, digitate hydroids, vermetid snails, parasites). The only fish from that tank, a percula, is presently living in a QT, having recovered from parasite treatment. My plan is to drain and scrub out the 30G tank, then start over with just liverock (no sand), the percula, and a RBTA or a couple corals. If I simply opt for brand new live rock, what's the most proper way to completely sterilize the old rock, so I could set it aside as dry base rock for future projects? Soak in freshwater and let it dry out in the sun?
<Bleach it first... ten percent laundry grade mixed w/ water; then freshwater, then air/sun>
In the alternative, if I opt to reuse the existing live rock in the new setup by “cooking” off all the bad stuff (i.e. 2+months in a darkened plastic tub, weekly saltwater changes, circulation, etc.),can I be confident that after the "cook", none of the hydroids, vermetid snails, algae and parasites will have survived?
<Not as good as bleaching.... Bob Fenner>
Chris
Re: Cooking live rock vs. new 4/29/15
Thanks, Bob. One follow-up question, if I may...How long of a time frame do you recommend for each of the bleach/water and freshwater soak?
<Dang! Is it faster to send you to look this up, read on WWM re; or simply to directly respond? Let's have you read:
Put the three words: "Bleaching live rock"... in any page. BobF>

Hi. Euxiphipops ID, and avoiding unwanted HH on DIY collected LR 8/30/14
Hi Bob,
<Adam>
A couple of questions which are not so easy:
1. I live near a coral reef and wanted to take some live rock for the various different type of coloured algae on the rocks. However I learnt the hard way before as my small fish were eaten by crabs that came inside the rock and ate the small fish at night in my tank.
<Yikes; yes>
Therefore if I fresh water dip the rocks and shake them for about two minutes hopefully this gets rid of the crabs which drop off but will it also kill all the lovely coloured algae defeating the whole object of taking them in the first place?
<I'd go another route here. Isolate the new rock in a separate system.... and try to bait/trap out unwanted hitchhikers for a few weeks. Such techniques and gear are discussed in the "Compatibility FAQs" of each group... e.g. Crabs, Bristleworms....>
2. This is a very difficult question: I have a tiny Angel which is about 1 inch. He is all good eating, swimming and is currently only in the tank with a tiny Emperor who is all good too. I intentionally did this so they can acclimatise and get to know there way around the tank. The problem is having looked extensively online and been an expert myself in this, is he a Blueface or a Sixbar. The Blueface has light blue bars between the white bars and the white bars of the Blueface are narrower compared to the SixBar Angel and the Blueface has three/four blue lines in the tail, which is not always the case as pointed out on your site back in 2009. Anyway my question is perhaps I have already answered it that there is not certainty
but when the Angels are this small do they get the white lines first and then the blue lines later?
<Usually the white is obvious first>
Maybe I am been too hopeful but he looks like a Sixbar but I am happy as he has the electric blue around the edge of his fins and still looks excellent but also online have seen pictures of what looks like Sixbar starting to change to Bluefaces.
<Ahh; only time can and will tell here>
Kind regards,
Adam.
<Cheers, Bob Fenner>

Blue-Green Algae/bacteria on live rock 9/28/13
Hi, first time writing although have read a bunch on your site, thank you so much. I have read much of your algae section but I couldn't find this described on your pages: if I have overlooked the answer, please feel free to give me the link I missed.
I am transferring 3 fish (clown fish, yellowtail damsel and yellow watchman) from my 33 gal tank to a temporary 20 gal, in order to set up a 45 gal with 30 gal refugium, Caulerpa, protein skimmer etc. I've otherwise had no issues with parameters, fish are fine. But my live rock has gotten pretty badly covered with black ("blue green") and red algae and I don't want it in the new tank.
<You'll either have to bleach/wash the rock (and let air dry) or leave it out for months outside and brush, freshwater rinse it...>
When I start setting up the new tank, if I scrub the LR under freshwater, not all the bad algae will come off.
<Nope>
If I put them in the new tank, won't this bad algae re-establish itself?
<Depends on the conditions there; but know that BGA WILL alter the conditions to suit it... and poison other types of life>
Or is it safer to just start from scratch, boil the LR until they look decent (I know killing all life), becoming base rock which means I would re-cycle traditionally.
<Yet another avenue. Yes. Whatever route you choose, I would use the existing rock as cleaned/abiotic base, and add a few pieces of new/fresh atop it>
Thanks for your help.
Gabe
<Welcome. Bob Fenner>
Re: Blue-Green Algae/bacteria on live rock 9/29/13
Amazing how quickly you have answered, thank you so much. I will bleach/air dry the LR. One last question re: this transfer. I have heard/read that the algae/bacteria is on the solid things (LR, glass, decor). Would it be risky to use a small amount ( say a cupful) of original water to seed the new tank? (Although the new LR I guess does the same thing?)
Thank you.
Gabe
<Spores will be transferred by anything wet being moved... but; they can even get here/there (thousands of miles inland!) via the air. Adding some will not do any harm. It's discounting the mass/majority that you want to avoid. Cheers, BobF>

live rock and hot water 3/17/13
Dear wet web crew,
<Lindsay>
After a recent cleaning I discovered that my tank thermometer had reset and missed a rise in temp to 84 from a normal 79.
<Likely not an issue>
I've since corrected the thermometer and cleaned the tank, but not until after a day or two with hot water and 2 lost fish. My other fish look OK and the water temp is back to normal, but my question is how long can live rock sustain hot water before significant die off?
<How hot? As in change in temperature?>
The rock is coated in purple coralline algae, and it looks a little less purple today (I don't know if that's a significant indicator or not). Should I be worried about keeping the rock in my tank?
<Mmm, good question... I'd be monitoring at least ammonia; be ready to pull it or the desired livestock if this becomes an issue>
Is there anything you recommend doing to support the live rock at this point, or just pretty much whatever damage is done and now just keeping everything in a normal state is all I can really do?
<The latter>
Thanks for your help,
Lindsay
<And you for sharing. Bob Fenner>

Dead Lionfish? And all else... saving LR 2/6/13
Hi there!
I was out of town for 3 weeks. A friend was feeding my tanks during my absence. Said friend neglected to tell me that my Volitans Lionfish died.
(Not sure how or why, as, he was perfectly healthy and all my water parameters were spot on.)
<Usually a very tough species... Most often killed by over and mis-feeding>
I came home to the rest of the tank's inhabitants dead, and there was a lot of froth at the top of the water.
<!?>
(I also saw a lot of food sitting in some areas..) I wore long reef gloves to scoop them out. I wanted to ask, is my live rock toast?
<Mmm, not likely; no>
This was a 200g aquarium, so I had an awful lot of live rock in it. Is there a way I can "clean" or "treat" it, so that I don't have to just toss it?
<Yes; I'd vacuum the substrate thoroughly, taking- changing out a good part of the water... refill and wait a few weeks>
I don't want to pass any toxin onto another tank (I am starting a new one)
but I also would really hate to have to get rid of it all. I know the froth had to have been the toxin from the Lion.
<Mmm, maybe, but likely just protein decomposition in general. If you'd like (I would) I'd run a few pounds of good activated carbon in your filter, water flow path... and a couple pads of PolyFilter if money's not tight>
I thought maybe soaking in fresh R/O would do the trick, even if it meant that it would have to be cured again.
<No need, use in such soaking>
Thank you for your time, and apologies if this was anywhere on WWM. For the life of me I couldn't find anything.
Lisa
<Take your time here. No worries. Bob Fenner>
Re: Dead Lionfish? 2/6/13
Thank you so much, Bob! You have no idea how relieved I am. Also, thank you for the speed-of-jet response. Goodness. Take care and thanks for all the incredible knowledge WWM provides. You're an awesome staff!!
<Ahh, welcome Lisa. BobF>

LR Question, Cu removal 8/2/12
I was surfing through craigslist and found 250+ lbs of LR for $60....so of course i was like that's got to be either a typo or someone is very desperate for space but anyway I clicked into the post and it said the LR is saturated in copper so i posted up on one of my forums asking if there is any way to possibly remove all copper from the rock and a few people came forward and said you could recure the rock at a low PH while running co2. Is this true?
<Can be done... I'd use an inorganic acid... like HCl... w/ good air movement if done in the house>
Is there any way to properly get rid of all copper from all LR???
<Not "all", but mostly all can be melted off thus; the rock used profitably as "base">
 ...if so i think this will more than likely be a very good
investment although time consuming. Looking forward to your response,
Thank you very much in advance.
<Please read here: http://www.wetwebmedia.com/baserockfaqs.htm
and here: http://www.wetwebmedia.com/curemovalfaq2.htm
Bob Fenner>
Re: LR Question 8/2/12
also forgot to mention that I had asked him how long the copper was ran and how saturated it is and this was his response " Rock has been saturated for over 1 year with a 3.0 level. Using Copper safe "
<Mmm, will make a wider-encompassing statement. Regardless of the format, all copper can be resolubilized by acidic reduction of the carbonate (faces of the rock) that it is adhered to. BobF>
Re: LR Question 8/2/12
thank you very much for your help I'm still on the fence about it...any other tips will be appreciated
<Keep reading. B>

algae and live rock quarantine 7/13/12
Hello there,
I have a 120 gallon tank with aragonite sand and about 100 pounds of base rock...no life...set up about 3 weeks ago. I bought a nice 10 pound piece of Pukani live rock
<Know the young gal it's named after>
and placed it in a 10 gallon quarantine tank with the intention of using it to seed my future reef, after 4 weeks of observation. In the past, when my base rock was live and in a prior tank (years ago), it was infested with every type of Caulerpa and bubble algae known to man and so my intention this time is to avoid these algaes in particular...hence the quarantine. I know it’s impossible to avoid every pest every time, but these I really don’t want in my tank because they can turn a relaxing hobby into a frustrating laborious affair! Well, 3 weeks into my quarantine, my rock has sprouted both Valonia and feather Caulerpa...hahaha!
<Yikes!>
Just have to laugh! It also has some type of algae that looks like individual flat top stools (the type you sit on) with tiny thorns, which may be a form of Racemosa but it’s still too tiny for me to accurately identify. So what to do? Is it basically futile to keep these things out?
<Mmm, at this juncture, you could go the biocide route... I'd use chlorine bleach if so. Read here re SOP: http://www.wetwebmedia.com/clnornart.htm
and the linked FAQs file>
I mean, I will definitely pick and scrub this stuff off and leave in quarantine an extra month but what if it sprouts again?
<"Only takes one spore">
Where does it end? Do I throw out a 90$ piece of rock with a ton of life...worms, pods, feather dusters, brittle stars etc?
<I'd isolate the live part... see if you can find, scrub off (outside the holding system) and rinse any pest part away>
The next piece will likely be the same! Should I clean it up and just place in my tank and accept that I will likely have some algae issues I will have to deal with? I thought this was suppose to be fun...a big sarcastic “ha”!
<Is one approach...>
Thanks much,
Dave
<Welcome. Bob Fenner>
Re: algae and live rock quarantine, alg. cont. 7/14/12
Hi Bob,
<Dave>
I now believe I have also identified Bryopsis hypnoides on this rock, and suspect that the little mushroom-like "stools" that I mentioned sprouting are Caulerpa nummularia, though they're still too small to be sure.
<Yikes! "When it rains...">
Also, when I first purchased this piece of rock I had placed it into my main system for the weekend with the intent to "seed" my tank.
<... including w/ the algae>
I had planned to incubate all future fish and corals, but thought it was unnecessary for the rock. After some more reading online I decided I should pull it out and quarantine which I did. This was about 3 weeks ago. Now getting to yesterday... the day after I wrote my first email to you, I noticed nearly all my base rock in the main system is sprouting the Bryopsis !
Life is amazing!!! It was only in there a couple of days but it was enough to spread all kinds of spores! I guess the good news is there is nothing alive in there besides the Bryopsis, so I have options.
I'm not sure I understand how to "isolate the live part" and yet kill the algae with chlorine. How do you isolate feather dusters, brittle starts, tiny snails, pods etc which are a part of\in the rock?
<Can't be done...>
Is it reasonable to think one can avoid the likes of Caulerpa, Bryopsis, Valonia etc altogether... or is it essentially futile and you just have to deal with them as part of normal maintenance?
<More or less the latter>
I mean if all this stuff is on just one single rock, how do people with 100s of lbs of rock avoid it?
<They don't really. Some are lucky... others have predators that help>
I would forget this rock and get another, but this could get expensive, and realistically I will probably get something in the tank anyways, if not now then through some spore that sneaks in with a coral in the future, and doesn't show itself until after quarantine. Am I right?
<Yes>
Finally, given that my main system is empty, the rock is not alive with anything besides bacteria and Bryopsis, if I drain the tank and fill with tap water, would that kill it and any other algal spores I may have inadvertently introduced?
<Hopefully>
If so, how long should I run it with tap water
before refilling with saltwater?
<I'd actually add bleach... let run for an hour, dump, rinse>
Please excuse the long winded questions,
Thanks for the help
Dave
<Welcome. Bob Fenner>

Re: FOWLR Fish stocking 6/1/12 6/5/12
<Hi Bob <<>>, Bobby. Could y'all take a look at this query. Poster is having issues with rocks leaching phosphates.>
Jordan, thanks for the reply and confirmation.
<Dave>
Back to questions on the "cook tank". I just received and used the
Seachem phosphate test instead of the API test and now have a much more accurate reading of phosphates.
I'm dismayed to see that after all the cooking effort, the phosphate level is still between .5-1 mg/L.
<What were the previous measurements? Levels are dropping, correct?>
This is after a heavy-duty mechanical scrub, 6 weeks of cooking, another heavy-duty scrub and a 100% water change. While I have no intention of doing more than a FOWLR tank, I'm sure I will be in for serious bad algae management issues without a drastic plan. Seems the "old tank rock" syndrome is not always willing to relent without serious measures.
<This is the problem of secondhand rock. You are paying for the previous owners neglect and from what I recall, the rock was in quite rough shape.>
I wonder at this level if a phosphate reactor is even worthwhile.
Seems I could spend hundreds or more on Rowaphos to achieve small ticks down on the phosphate meter over time.
<Bulk GFO will be a cheaper option. Small ticks add up but I agree it is not an acceptable solution at this point.>
So, I am back to square one on plan of attack, and wondering whether I should either a) plan a Rowaphos/reactor approach in combination with macro-algae harvesting,

b) just acid wash the rock and start over, or
<I'm not a muriatic fan; I'm going to defer to another crew member.>
c) continue the cooking for much longer,
<Slow but safe option.>
or d) ?... I believe Bobby and possibly even Bob weighed in at some point on suggested approaches. Could you mull this over with the Crew, and let me know what you suggest?

<Jordan>
Re: FOWLR Fish stocking 6/1/12> 6/5/12
So, I am back to square one on plan of attack, and wondering whether I
> should either a) plan a Rowaphos/reactor approach in combination with
> macro-algae harvesting,
> 
> b) just acid wash the rock and start over, or
> <I'm not a muriatic fan; I'm going to defer to another crew member.>
> c) continue the cooking for much longer,
> <Slow but safe option.>
> or d) ?... I believe Bobby
> and possibly even Bob weighed in at some point on suggested
> approaches. Could you mull this over with the Crew, and let me know
> what you suggest?
> 
> <Jordan>
<<I wouldn't acid wash (and rinse, then soak) this olde rock unless you intend to add a considerable (a few tens of percent) of new to inoculate, re-seed the biota that will be entirely eliminated. Have you read here: http://www.wetwebmedia.com/lrselfaq2.htm
and the linked files above? Bob Fenner>>
Re: FOWLR Fish stocking... now HPO4 control 6/5/12
> Bob and Jordan, thank you. It seems the phosphate levels have stayed
> the same despite the measures taken over the last 8 weeks. This is why
> I have given more consideration to the drastic acid route. I would be
> prepared to follow Bob's suggestion on a complete reset/reseed of ~20%
> live rock to start anew.
> I did read/reread the page Bob sent and the linked files, and one
> aspect I previously didn't consider surfaced. The pH consistently
> measures around 7.9 in the dark "cook tank", perhaps a pH adjustment
> may add prevention to phosphate release from the rock? Do you think
> this plus bulk GFO plus other measures (skimming/macroalgae) would
> yield a continued noble but fruitless run? I just wonder if more
> time/$ will not help me achieve a more acceptable continuous phosphate
> range.
> Ye Olde Tanke Rocke!!
<... Best of all is a long term, "holistic" approach, using macrophyte et al. culture, as large a DSB as possible... perhaps Ozonation... B>
Re: FOWLR Fish stocking 6/1/12 6/5/12
Bob and Jordan, thank you. It seems the phosphate levels have stayed the same despite the measures taken over the last 8 weeks. This is why I have given more consideration to the drastic acid route. I would be prepared to follow Bob's suggestion on a complete reset/reseed of ~20% live rock to start anew.
I did read/reread the page Bob sent and the linked files, and one aspect I previously didn't consider surfaced. The pH consistently measures around 7.9 in the dark "cook tank", perhaps a pH adjustment may add prevention to phosphate release from the rock? Do you think this plus bulk GFO plus other measures (skimming/macroalgae) would yield a continued noble but fruitless run? I just wonder if more time/$ will not help me achieve a more acceptable continuous phosphate range.

Ye Olde Tanke Rocke!!
<Jordan>

Cleaning Dry Rock 4/15/12
To whom it may concern,
How are you? Thank you for taking the time read my query!
<Hello Brent, and you're welcome.>
1 year ago a tore down my 90 gallon aquarium. I dried out my rock and have stored it in 2 Rubbermaid containers.
I am in the process of starting my 90 up again <and> I would like to know if I should scrub the rock down with a vegetable brush in water before I place the rock in the aquarium?

Would the water need to be RO water? Or could I use tap? I live in Calgary, Canada. I have asked around on my local reef forums and it is split down the middle as far as water quality goes in the city.
<If you mean RO water for your tank, use RO if city water is questionable.>
Any advise would be greatly appreciated.
Thanks again,
<You're welcome. James (Salty Dog)>
Brent
Sent from my iPhone
<Mmm, would take too long to reply on my iPhone....small keys, fat fingers.>

Concerns - new setup with used rock/equipment 3/24/12
Crew,
<Dave>
Looking for some thoughts on my situation...
I acquired a 135G tank (with 15G sump), with 130# LR and about 50# LS.
After cleaning all equipment meticulously, and also a thorough cleaning of the LS (with water and removal of any cloudiness/detritus etc),
<Cleaning used sand is a hassle but necessary if you want to re-use it. Good job!>
I restarted the tank with the "old" water.
<Unnecessary and possibly a bad idea depending on the waters quality.>
The LR was left to dry for a few days during the process, by the seller, before being restored to a "wet" state.
<Uh-oh!!! Every living organism within the rock died when it was allowed to dry. That is a very large amount of dead organics; rock needs to be rinsed and cured.>
I also discarded all other old filtration.
After completing the build and seeding with 40# of cured live rock, with plenty of life and some macro-algae, I tested nitrates with several kits and got a wide range of answers but decided a massive water change was due.
<Water changes are not going to accomplish much with the amount of dead organics trapped inside the rock. You are going to have to wait for the tank to fully cycle at this point. Read more on biological cycling--
http://www.wetwebmedia.com/estbiofiltmar.htm >
I removed 80G, replaced 40G, and tested nitrates at 120-160ppm (or possibly higher). I moved 30G to my QT tank and did a 90% water change, and still tested at ~120ppm nitrates (6 hours after the water change). I will retest again 72 hours after the change (could the LR have released nitrates into new water stir-up from the change?), but am concerned with the biological quality of what I acquired at this point and wonder if I should just start from the beginning.
<You acquired 130# of uncured rock. You are starting from the beginning.>
The prior owner did run the tank for ~10 years, and there seemed to be some lagging care at the end of his ownership.
Do I do a 100% water change only?

Or do I do this and also bleach the rock (is it possible that the old rock is "leaching" massive nitrates into the tank?)
<The old rock is uncured and is producing ammonia. The rock may be loaded with phosphates due to the previous owners lack of care. Bleaching may help remove some of the phosphate.>
I am doing a FOWLR setup, with very hardy specimens (who will be dipped/QT'd per WWM guidance), so I am not necessarily targeting 0ppm nitrates.
<Good call on the dips and QT but I would recommend waiting until nitrates are at least near 0. No reason to start with less than pristine water before adding a bio-load.>
I will also use Caulerpa in the sump.
<Caulerpa has many pros and cons. Read more on Caulerpa sp. here-
http://www.wetwebmedia.com/ca/volume_6/volume_6_4/caulerpa.html >
Also, the skimmer (which hasn't yet been used due to replacing the pumps)
seems rather large - two 700gph Danner Mag drives - so I will employ strong nitrate reduction through the tank life. Hm, thoughts?
<Can't over-skim a FOWLR.>
Sorry for writing a novel. Grateful for your patience.
<An easy read. Proper spelling and punctuation are much appreciated.>
Dave
<Jordan>

Moving/Cleaning Rock 6/5/2011
<Hello Brent>
Thanks for your time in responding to this email.
<You're welcome.>
I hope you are well.
I tore down my tank 2 months ago. I dried all my rock on my deck for 4 days and then packed it up in a Rubbermaid container. There is 50 lbs of Marco rock, another 30 lbs of Fiji rock and about 40 lbs Pukani rock that was in my aquarium for the four months that it was up and running.
I finished my move and now I am going to set up my 90 gallon aquarium in the next month or so.
I am doing a foam rock wall to cover the overflow with a bridge connected to an island.
The rest of the rock will be in the sump.
After reading over RC I see that some people use bleach and then acid to kill the organics and phosphate on and in the rock.
Should I be doing something like this before I introduce the rock back into my aquarium?
<In your case this procedure isn't necessary and is time consuming. Just scrub the rock good with a stiff brush, hose down well and allow the rock to dry on your deck.
Allowing the rock to sit in the sun for a week will in essence bleach it.>
Thanks
<You're welcome. James (Salty Dog)>
Re Moving/Cleaning Rock 6/5/2011
Thanks for writing back so quick!!!
<You're welcome.>
Should I use RO water or could I use tap?
<For cleaning/rinsing the rock, a garden hose with nozzle is all that's necessary.>
Thanks again
<You're welcome. James (Salty Dog)>
Re: Upgraded Tank, starting to get an interest in Corals, am scared of making the wrong decisions! Also a quick question on water storage. 6/6/2011
Sorry James .. the water storage question was from a previous enquiry!
<No problem>
can I rinse in tap water? or will the chlorine be bad for the tank?
<Shouldn't be a problem.>
thanks for your help
<You're welcome. James (Salty Dog)>
Martyn
WWM... help?
Upgraded Tank, starting to get an interest in Corals, am scared of making the wrong decisions! Also a quick question on water storage. 6/6/11
Hi again James
Kind regards, And please extend my appreciation to everyone for such an informative web site!
<Mmm, do not see any question on water storage.>
(by the way, I am a web developer by trade if you ever need free help!)
<Oh, Bob may be interested in your kind offer of help if needed. James (Salty Dog)><<Thank you for your offer Martyn. DarrelB is coming down to visit in person... to likely read me the high-tech riot act re how backward the site (actually myself) is. We'll see. BobF>>
Martyn
Look...if you don't want to make mistakes, buy a book that was recently published and preferably by a noted author. The "New" version of Conscientious Marine Aquarist by our own...and personal mentor... Bob Fenner, is a great start!
Find a local "Reef" store that has successful displays and a knowledgeable staff and start asking questions to bolster your basic background on reefkeeping! If you are leery of any advice, just ask us here at WetWebMedia!
Cheers,
Sam Scalz