Hey everyone. I have two healthy, strong Kribensis that i moved from my 46 gallon tank to an already established 10 gallon tank so they could have it all to themselves. I put them in with 1/3 of their own water 1 week ago. Since the switch the fish have had very poor behavior and have been very sluggish. Repeated water tests reveal nothing obviously chemically wrong with the ten gallon tank, after all, it has been running for almost a year with 8 fish, its former inhabitants were moved to a different tank.

I have compared water tests between the new 10 gallon tank and the old 46 gallon tank and the tests are exactly the same, with the exception that the new 10 gallon tank is a little more alkaline. I should also mention that the 10 gallon has a sand substrate, whereas the 46 gallon was dirted with gravel.

The fish are really struggling and the only major difference seems to be the sand bottom on the new tank. Are there different bacteria populations that reside in the sand? Is the sand effecting their water chemistry to the point that they are struggling, but nothing has shown up on the test strips? I dont really know what to do, i'm considered getting new substrate because that seems to be the only variable that is uncontrolled.

Please help, my poor fish are sad in their new tank. ;(