Sick Krib maybe a sick clown

[thetexasranger]

I have a 4 in krib that in one day became very ill. I noticed that he suddenly became extremely shy and lethargic. This is usually a very active fish that I've had for over a month. He is favoring its left fin...he can use its right one and it while it doesnt seem damaged its not using it as much as the other. As of now hes hiding in a corner and is not moving. It has somewhat elevated gill movement. I can tell you while I only feed every other day...this fish eats far more than his share despite my efforts...he may be bloated but I do not know. I did not add anything to the tank and I do 25% changes per week. I lost some clown loaches (4 to be exact) which had issues swimming recently (they too were extremely lethargic) but I thought it was because they were sensitive to the water. Other fish seem great asides from 1 krib and 1 clown at the moment.
I also wonder if I have aeration issues. I dont have a powerhead (any recommendations? I dont even know how to install) so I'm relying on my emperor 400 for oxygenation. Could this be part of the problem?
My water readings are as follows:
Ammonia: ~.10 (my tap water has trace ammonia and I just did a water change)
Nitrite: 0
Nitrate: 10-15
ph: 7.5

 

[damian09]

sound like ya have water quality issues m8 but im no expert how long has ya tank been set up 4 and do ya use a gravel cleaner

 

[RexyTexel]

Do you use a water conditioner when you do your water changes? And are you adding it before or after the new water is placed in the tank?

If the fish are gulping at the surface then you'll know you have oxygen issues. What temp. do you keep your tank at?