Is my fish sick or pregnant!?!

[Fishlove]

Hi,
I have 2 blackmoors in my tank! Recently I have noticed that the smaller one (buddy) is chasing my bigger one (Keith). Whenever I am near the tank Keith usually hides and won't come out! I've noticed he's got a bit fatter and he hasn't been eating properly! He usually plays with his food and then spits it out! His breathing has got heavier and he hangs at the bottom of the tank!
I don't know the sex of either of the fish but I'm not too sure if he is pregnant because I have only had Keith for about 6 months and buddy only 3 months and they are still quite small! I have recently had to treat my aquarium with fin Rot but seems to of cleared up! Also the fish are usually at the top of the tank but I turned the filter up and cleaned them out and they don't seem to do that anymore!
Any advice would be great thanks!!

 

[jlk]

Hi! We need some more info in order to be able to help! What size is this tank? What are your exact numbers for ammonia, nitrite, nitrate & ph? What are you using to test (liquid or strips)? What is the temp? Is the fish that looks 'fat' have scales sticking out like a pinecone? How big are the fish? I would suggest start by doing a 50% water change asap and do another anytime you notice the fish acting 'strange'. Make sure you temperature match and properly all new water!