I have a Fahaka, about 8" and just got an Mbu about 3". I have a colony of marbled crays and MTS but know I need more and am going to buy as little as possible from the grocery. Do any of you guys raise freshwater clams to feed your puffers? (Corbicual sp.) The literature says they get about 2" and if they grow fast enough I was hoping I get grow a good amount in a 20L. I have read just enough to get my curiosity going. I am looking for them to grind the beaks as much as a food source. Any experience you can share would be appreciated.