Blue Flash Cichlid

[wrightt3]

I recently picked up a blue flash cichlid (Thorichthys aureus) but he was outcompeted for food by the larger cichlids in the tank so I temporarily moved him into 20 gallon tank and was wondering at what size I should reintroduce him. I want him to be at a size where he can hold his own but I don't want to leave it too long and have him become stunted in the smaller tank. The 20 gallon measures 60x30x40cm. Inhabitants in the larger tank include an angelfish and a pike cichlid (proteus I think) both of which are about 5 inches long. Any advice would be appreciated. 

 

[KieranBoyne]

When he is of a similar size, or at least 3/4 I would say.