Height of sand - 27/04/06 I searched for a formula to show how many lbs you need to equal so many inches of thickness in a certain area.  I can't find that formula, can you help? <Hi Keith. It's easy to do this sort of thing if you use SI units as opposed to inches and lbs. Volume = mass/density, and Volume = tank area * height. Hence The height of the sand in your tank = mass / (density * tank length * tank width). Here, all lengths and widths are in metres, and mass is in kg. You'll need to search for the average density of the type of sand you wish to use, in kg/m^3. "density of sand" should be a fairly straightforward Google search. Best regards, John.> Thanks

How Much Gravel? Mike, It's me again.  I forgot to ask......what would one consider the optimal thickness or layer of gravel to "house" my bacterial friends in this 29 gallon (roughly 30" wide x 12" deep) tank? Thanks, David < For optimal bacteria growth they need oxygen to complete the process. Any more that a couple of inches doesn't do much good if the oxygen can't penetrate.-Chuck>

FW substrate depth Hello all you Wonderful WetWebMedia Warriors. <Hello, just finished up an attack on a Corallimorph.  Next stop the LFS for battle royal.> I have a 29g FW with a Powerhead402-driven UGF under an Eclipse 3 hood. Tank is populated to about 1.25 inches/gal, and is over 5 years old with 1 fish of that age and most others over three years old. Assuming I can't be doing anything too hideously wrong, I'd still like to create the best environment for my wet friends. As a result of combining tanks a while ago, two things happened:- 1) I have a little over three inches of gravel substrate. Is that too much (i.e. detritus trap?). The powerhead output is certainly significant. <Under gravel filters by nature are a detritus trap especially if they have been running for a while.  Be sure to vacuum the gravel during water changes.  3in is fine as long as it is consistent throughout the tank.  If the power head is on one of the uplift tubes and there is something less powerful on one of the other ones (i.e. an airstone)  the power head could be sucking water down through the other uplift tube instead of through the gravel.  Path of lease resistance and all that stuff.> 2) Fully realizing this is not an optimum situation, I have a 4" pink  albino Cichlid in with my community fish. His two buddies passed away over time, one when they were together in a 20g long, about a year ago, and another about 6 months after moving the two remaining fish to the community tank. I can't easily justify a larger tank just for him, but I'm really not sure he's happy.  Do you have any recommendations for either of the above situations? <I'm not sure what is in your community tank besides the cichlid, but it would be good to examine the water quality needs of each of the fish, chances are the cichlid has different needs.  Cichlids are also known to wreak havoc on undergravel filters with their love of digging.  Maybe you could justify a bigger tank for the community and let the cichlid keep the 29gal?  Best Regards, Gage> Thanks!