On Tue, 3 Mar 1998, Kathryn Olson wrote: > We had the same problem with one tank, turns out the gravel had > fine/crushed sea shells in it. One test for that is too take a sample > of gravel (not too wet) and add vinegar too it and see if it bubbles. > > We now don't use that gravel in the APisto tanks, save it for the > Africans. > > Erik may recall the name of the gravel, but I don't. It was > specifically being sold for aquariums as well (Texas ?) Lapis Lustre. It didn't add too much hardness to the water, probably for most folks it'd be a good thing, adding a little pH stability. But not good for "why isn't the pH dropping to 5 like it should?!" us. The place that sold it in bulk actually labeled it as aquarium gravel and also acknowledged that it had shells. Nobody had ever mentioned to them that this might be a problem. - Erik - --- Erik Olson eriko at wrq.com