Oxygen issues caused red belly and upside down floating

[Cuffep]

Hey, I have a discus fish problem. NH4, NO2, NO3 are all stable throughout the story. Ph is 7.8, I know its high, the fish seem fine since I got them. Temp around 27c. Raised to 28c after water change yesterday. Got it down to 27 again after I saw the problem. Mightve been a part of it all.

Planted and cycled (a year) 60g tank with some dicuss and an angelfish couple. Weekly 20-40% changes. Moderate feeding as they are small. No CO2!

I had a green dust algea problem for a month or so as I was figuring out dosing requirements. As I stabilized it, I didn't scrub the glass for 20ish days, so that the spores have completed their cycles and I could scrub out it in thicker layers and remove it successfully.

But, because I figured out the nutrients, the algea kinda died on its own and as snails ate it, it didnt really come back.

Well, yesterday it was finally time to scrub out the glass.

I did so, and small parts of hardscape and did a 50% water change.

This morning, I wake up at 5am for work and see snails running to the surface and fish struggling with oxygen. I guess, its a combination of the water change and I've accidently covered too much surface area for proper gas exchange.

Added air stone and did 25%ish water change.
All fish stabilized a bit as I went out for work.

Found one discus dead.
Two are in a bad condition.
Both are floating upside down, stuck somewhere around hardscape as they appear weak.
One however, is worse as it has a red swollen belly

I cant do anything more as Im at work for a 12hr shift and left them be instead of rushing to set up a hospital tank. They werent getting bothered by other fish.

If the red belly is still alive when I come back. What do I do, what medicine is best in this case if I would want to use it. Any other advice?

[Cuffep]

Pictures

[Second Hand Pat]

Hi Ivan, my first thought is do you have chlorine/chloramine in your source water? If so did you add a dechlorator to the tank? Also what type of filtration do you have (sponge filter, sump, HOTB) or how do you add oxygen to the water?
Pat

[Cuffep]

Hi Ivan, my first thought is do you have chlorine/chloramine in your source water? If so did you add a dechlorator to the tank? Also what type of filtration do you have (sponge filter, sump, HOTB) or how do you add oxygen to the water?
Pat

Fluval 307 performance canister filter

I use prime, as I'm pouring water in, I dose prime. I do not dechlorinate in a bucket. Water rarely has chlorine, but it does.

I also have an elongated airstone on really low flow, I turned it up when I saw the issue.

Problem is, as to why I suspect oxygen, I usually fill my aquarium nearly at the top. This time, I overfilled it.. as I saw that half the surface was touching the glass lid blocking a lot of surface gas exchange.

I think its a combination of a water change, loss of biofilm/algea which destabilized the aquarium and the gas exchange.

Is it best to leave the discus alone, I've turned off lights for today, nor will I feed. Is a quarantine tank a good option, usually fish stress so much with moving to a hospital tank that I want to leave it alone.

[Second Hand Pat]

How long was the canister filter was off while you were doing a water change and tank clean up?
Pat

[Cuffep]

How long was the canister filter was off while you were doing a water change and tank clean up?
Pat

It was a more intense clean up than the usual 20-30minutes due to the algae.
About an hour, then I turned it on for 5ish minutes and another hour, maybe even hour and a half.

Now that you asked me this. Maybe such a long timeout was the main culprit? and the 5ish minutes break with the power on werent much helpful.

[fljones3]

Did you clean the gravel? Gases build up in the gravel over time. What seems to be a success and stable for 3-6 months can cause such a calamity. Your canister might have contributed but the gravel is my guess. Sorry for the loss. Grievous.

[Cuffep]

Did you clean the gravel? Gases build up in the gravel over time. What seems to be a success and stable for 3-6 months can cause such a calamity. Your canister might have contributed but the gravel is my guess. Sorry for the loss. Grievous.

Nope, did not touch the gravel aside from replanting a couple of stems.

[Second Hand Pat]

Nope, did not touch the gravel aside from replanting a couple of stems.

Frank has a point. When you replanted your stems was any bubbles released from the substrate?
Pat

[Cuffep]

Frank has a point. When you replanted your stems was any bubbles released from the substrate?
Pat

No, just some detritus. Maybe Ive disrupted enough to cause an issue. But then again, it wouldnt be such a simple solution as the fish being stabilized 10minutes after 30ish% water change and better oxygenation right.. aside from the already sickly fish. I dont know, very peculiar, as I didnt see any red gills, just half of them with surface gasping.

I'm honestly scared of going home and possibly seeing the two distressed discuses dead.

[jeep]

Are you aging your water?

[Cuffep]

Can it possibly be dead cyanobacteria? When I scrubbed the back glass (first time in a long time), there was a thick layer of dark/black substance like cyanobacteria BUT it did not have the foul, swampy smell, no smell what so ever. Im not sure what bacteria that might be.

There was some reddish like cyanobacteria on the hardscape as well but not nearly as much as the back glass.

I grabbed what I could with my tweezers, but most was left in the water.

[chelltom]

Any updates on this ??

[dspeers]

I think maybe you were right and the O2 diffusion was disrupted by the tank being overfull. Your tank is heavily planted and although plants are net O2 producers during the day, they are consumers in the dark such that heavily planted tanks need additional aeration relative to non-planted tanks.