Red Gill Help

[twincessna340a]

As a general synopsis, all the fish in my tank have developed the red gill. I confirmed this while observing one for another reason and looked into all of the gill which was completely red. I first noticed it in my Oto, but I seen pictures of "healty" Oto's with that coloration so I first thought it was just organs until I saw them in my Mosquito Fish, even in the MF I added about 6 hours prior. My Sailfin Mollies don't seem to be affected that much. They all seem to be acting normal: active swimming, full display of fins; active eating; active schooling; constant pooping all colors but white. They occasionally swim and hang near or on the surface of the tank (especially when I leave, but they live on the surface in my lagoon) My tanks is doing well too: my water is as clear as it ever has been, my gravel is significantly cleaned, feeding habits improved.

As a note: the Molly I introduced today might be sick - dorsal fin damaged; its sluggish, poor appetite, and has a red spot similar in color to the others at the base of its body near the fin. I put it in a breeder for observation.

1) 1x-Md Oto; ~10x Adult Mosquito Fish; 2x- Adult Sailfin Molly (all but Oto being wild caught from my brackish lagoon)
2) Ammonia-practially 0 ; Nitrite-3ppm; Nitrate-10ppm; pH-~7.7; Temp-78-87; KH-180; GH-120 (temp varies as its on a screened in porch in the shade...lagoon temp is at least 88 and reads 90 during the day also it has slighty higher pH, KH, and GH)
3) 20g tank about 1 month (with a 4" Java Fern since beg; another 2x 4" plants added today) Started as brackish, slowly weaned off salt...off salt for 3 weeks; just added light salt with major w/c to help 1 Molly brood. Aerated with 40g pump with 2 large airstones
4) Aqueon 10 & AquaClear 30 (after about 1.5 weeks)
5) Did a ~60% wc this afternoon, previously theyve been ~30% every 3rd day; use water conditioner; change filters as needed; vacuum gravel every time
6) Most MF since day 3/4; oto 4 days ago, 1x MF 1xMolly today
7) 2 4" Plants
8) Quality Flake Food; Occasional Bloodworms

Last thing I did before writing this post was changing both filters.

Please Help! Thanks!

 

[krap101]

Well, it either sound like ammonia/nitrite poisoning, parasites, or maybe some sort of aggression. I've heard that mosquitofish are normally pretty aggressive, but most fish ignore otos, so that might not be the case. I'm guessing the temperature swings aren't helping. All this is speculation, so some pictures would help

 

[dkpate]

Welcome to AA.
Yes, you should have 0 ammonia, and 0 nitrites, as both of those will kill your fish. You will need to do a partial water change (pwc) every day until they are at 0 if you want to try and save your fish. I would only clean half the gravel until your cycle is finished.
Don't change your filters unless they are falling apart, that is where your good bacteria lives. You can just rinse them off in old tank water if they get gunky.