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How deep is your tank, what T5 fixture do you have, type of clam you want?
I have a derasa admittedly the least light craving of the bunch and it is growing like crazy under 8X54W T5 120G 24in deep tank. You can probably keep any clam you want depending on the setup .... feeding helps too so you can offset lighting to a degree.
I don't feed mine a ton to be honest.