I'm interested in the clams for their filtering ability, thing is, how many is "just right"? Assuming a 55 gallon tank, what is a good number to ensure clean clear water, but they all get enough nutrition?

And any experienced people, how good are they at their job anyway? Have you noticed much improvement since getting them? I doubt they'd ever replace an external filter, but extra cleaning never hurts.

The problem with freshwater clams is that you never know if they are alive or dead. They also feed on freshwater plankton that isn't normally present in your tank. I suspect you will need to supplementally feed them like Corals or Giant Clams. I have only seen them once in the wild and their water environment was very clean and pristine.

I've had 4 freshwater clams and I'm down to 3. Was down to 2 then another one showed up magically. As stated it's hard to tell if they're alive or dead, unless my shrimp discover them dead then they'll dig it up and have a feast. They like dirty water and VERY dirty substrate, especially sand. Think about clam beds in the ocean, and how stinky they can get.

My advice for keeping clams:
1. Water quality goes out the window. However, not only will your clams thank you, but your plants will as well. Filters and clams don't get along well.
2. Don't touch the substrate. I've seen my clams dig themselves all the way out of the substrate then right back in. And, as stated, they love dirty substrate.

Not sure what they like for water parameters and temperature, but mine seem to be doing great with tropical environments.

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Officially fishless until after the move....tune in later for details!