You are here:

Freshwater Aquarium/Cichlid Cotton Wool Disease


Hi Rich,

Since you have had tanks for so long, I figured you would know about some of the diseases that come with them. Right now it looks like I have some fish with Cotton Wool Disease.  It started with one of my Peacocks and spread from there.  Symptoms are white blotches near fins but on body, no white around mouth yet, but what really made me think Cotton wool was how frayed the fins are on these infected fish.  So  based on my analysis I disinfected all of my rocks and took all of the substrate out, disinfected the siphon on my filter and the inside of the filter.  pretty much started over.  all of my fish are still alive but this spreads so quickly that I'm not sure how long they will last.  Right now I took out active carbon and am treating with mela and pima fix with constant water changes 15%.  Is there anything else I can do or should I just try to wait it out and continue with treatment?  I heard copper sulfate formulas work and I want to try and pick up some aquarium salts but haven't done so yet.  If you know another method that is successful can you share it with me.  I love my fish I don't want to lose them even though this disease is ruthless.

Thnak you
Tom M

Hi Tom

Actually I've never had any major diseases or internal or external infections in any of my tanks. I take great care of all my fish. I do however know about the most common diseases in tanks through helping people on this site and doing research.

What you're dealing with is Fin Rot. I would continue with the Melafix/Pimafix treatment following directions on the bottles for using both in combination. DON'T mix any other medications in with them. Over medicating does more harm than what you are treating. I would also add some aquarium salt to the tank, 1 tbsp per 5 gallons of water. Make sure you use Aquarium Salt and not table salt or any iodized salt.

It sounds like you're doing 15% water changes while you are treating the tank. By doing so, you are removing the medication from the tank. A 50% water change should be done prior to treatment, then no water changes during treatment. Then another 30% water change after treatment and replace your carbon. Then 25% water changes every week.

Another mistake you made here was removing the substrate and disinfecting your filter and rocks. Doing this did nothing but kill off the beneficial bacteria that your tank needs. So basically it will likely start cycling all over again.

Finally, most fish diseases and infections can be prevented by proper care and regular tank maintenance. 25% - 30% water changes must be done every week and make sure you siphon the substrate to remove excess food and waste. Replace the carbon in your filter every month. In my Cichlid tanks, I actually do 30% water changes on weekends then another 15% water change mid week. Cichlids tend to be a little more messy than common community fish. Also make sure you maintain proper temperature. Cichlids need a water temp of 80-82 degrees.

Another factor in preventing diseases and infections is diet. Cichlids need meats and greens in their diet. TetraMin Tropical Flakes and Tetra Cichlid Flakes will provide them with the proper nutrition they need. Do NOT feed them pellets. Pellets tend to expand before they are digested and cause constipation and other problems.

I'm not trying to imply you don't take care of your fish, but Fin Rot and all forms of Cotton Disease (Cotton Wool, Cotton Mouth, Columnaris etc) is caused by poor water quality.

I hope this helps get you back on the right track, good luck!


Freshwater Aquarium

All Answers

Answers by Expert:

Ask Experts


Richard Hight


I own and maintain several freshwater aquariums from 2 to 180 gallon. I can answer most questions about freshwater aquariums, including setup, cycling, maintenance, compatible tank mates, feeding. Moving? I've moved fish both across town and across the country and can help you get your little aquatic friends to their new home safely. I know and have experience with most freshwater community fish, South American Cichlids and African Cichlids. I don't answer questions about Goldfish or keeping Goldfish with Tropical Fish. I also don't answer questions about keeping crustaceans (shrimp, snails, crabs etc) with Tropical Fish, nor questions about saltwater fish or aquariums. I'm not available to answer questions on weekends, this is when I do maintenance on my own tanks.


Many years of personal experience with community tank fish, semi-aggressive fish (Barbs, Tetras, etc), Angels, South American Cichlids and African Cichlids.

HSG 2010-2011 prof

©2017 All rights reserved.

[an error occurred while processing this directive]