True enough, Eileen has 6 clams vs my 12 in the same size tank (120). She has much more water volume while I have way more live rock work in my tank. That maybe a factor.
I do a 5 gallon weekly change and I think she does a 30 gallon change?
Also I think the type of clams make a difference too. I have 2 hippo, that hardley seem to grow. 1 crocea that seems to grow slow. 2 large gigas that seem to grow relativly quickly, 2 large squamosa, and 5 deresa all pretty small, but seem to grow well too. Her clams are 1 deresa, 1 squamosa, 4 croceas?
My tank is pretty establish as well about 4 years old now... and some of the rock and corals are about 8 years old from my older tank.
I haven't tested my nitrate so I am not sure.....but just because my 1 tank seems ok with just clams, it is in no way proof that they help alot. So for all of you who want to get more clams for filtration, read up first and maybe try to get other peoples input.