Cichlid fish/tank problems

Question
Hi Chris,
First off, we had have this tank running for about 2- 2.5 years. I think it is around 97L-ish. We have a 1 Cichlid (not sure what type, but not an African Cichlid) and 1 Platty/ bottom feeder. We did have a couple more fish, but the Cichlid killed them. This is the only Platty who has been able to hold his own & survive in the Cichlid's presence. We have a Aqua-Tech 10-20 filter. pH is around 7.5, Ammonia is around 0 ppm, we have no test for Nitrites. We change the water one a week, I think around 25% (my Dad has been the one carrying for it for the last 2 years, since my brother left).
Question: We are having tank cloudiness problems off and on for atleast 1 year. And now it seems the Cichlid is sick. Cloudy eyes, with a dusty/white/slime on his head and portion of the body. He must have HITH (I was researching it on the internet last night) for the whole time we have had it, no did not know it was a disease. He is not eating and had abnormal behaviour. This once aggressive fish always poking at the Platty, sits at the top of the tank in a corner. The top of his body partially out of the water, the top fin looks like it is flat on his body or missing. Please help, where should we start?
My game plan: I have added some aquarium salts, Crystal Clear and Stress Coat. We did one treatment of an anti-fungal medication yesterday (with a Carbon filter, we can not turn it off???). We plan on doing a 25-30% change tomorrow, and start with an Anti-bacteria treatment.

Answer
Hi Tianna;

Sounds like you are doing a great job. Excellent effort in doing research and finding remedies too! You are doing the right things for sure. Do the water change and start with antibiotics tomorrow as planned. If your carbon has been in use for more than a week already don't worry about it. It becomes totally clogged so it won't absorb any more medicine than your gravel and decorations would anyway. It only works when really fresh.

Vacuum the gravel too when you do the water changes. There could be a lot of crud in there causing problems for him too.

Keep up the good work and let me know how things are going!

At Your Service;
Chris Robbins