How much food for a tank with no fish?

[fronty]

12 gallon nano

Livestock

hermit crabs
pistol shrimp
small dendros
hammer coral


I had a watchman goby and clown fish. I ended up selling the clown fish because he started attacking the goby. The goby become stressed and ultimately died.

I'm not really interested in getting any new fish. How much food should I feed the crabs and pistol. I was feeding spirulina every other day to the fish. Food recommendations??

 

[Sk8r]

1 flake per gallon of tank, reckoning flakes the size of your little fingernail.

 

[fronty]

1 flake per gallon of tank, reckoning flakes the size of your little fingernail.

How often should I feed them?