5 gallon with damselfish?

well i have 2 heaters which are both tetra brand forgot the watts on the larger one but it seems to be doing fine and its manual not automatic which i perfer

 

Why don't you use a HOB filter for flow?

 

"bio-wheel Power filter penguin 100" as they call it

 

so no need for the power head i take it then? and one more thing
i have a nano protein skimmer the tank is 2 weeks old and no sign of high cycling rate i got some good sand from an lfs already used washed it and the live rock i scrubbed and clean too still no nitrites or nitrates i dont have an ammonia test kit figured it would be the same diff as nitrates and nitrites anyway
so would it be too early to add the protein skimmer? or should i just take the power head out and add the protein skimmer?

 

i have 3 damsels in a 75gal and they're already territorial and fighting everything else in the tank. im pulling them out today (they were in there for cycling purpose anyways)..

anyhow i wanted to say two things... 1) theres a damsel at my LFS thats a full 3.5" long and 2" tall. so yes i would stick to one 2) my damsels attack and nip at anything i put into the 75gal so again confirming their being territorial/aggressive

 

also true. my true percula clown likes to linger in one area of the tank unless its hungry