Sudden discus death

[Boby]

Hello,
I bought 10 leopards 2 month ago. First month I put them on QA. Everything looked fine. They are about 3" right now.
Yesterday I noticed they changed their color(became dark) and were very stressed. They were jumping and crashing. Breathing rate is very high. One of them has part of the body very dark on one side and the other side color is normal. Today in the morning I lost one of them.
To rule out intoxication I did massive water change 70% and increased temperature to 90F. I fed these fish with the same food that I used for all other fish so I think food poisoning can be ruled out as well. Some fish I isolated in 30G tank with salt and formalin& malachite.
I'd like to know if anybody else had the same symptoms or have any suggestions.
Please see all details below.
Thanks, Boby

----------------------------
1. visible parasites (describe)
None
2. stringy feces
None
3. head standing
None
4. bloated/ constipated
None
5. Hole in the head, lateral line erosion
None
6. spots, salt like flecks, velvety appearance,cotton like
growths etc.
None
7. excessive slime production
None
8. labored breathing, disfunctional gill
Yes,
Didn't see any disfunctional gill
9. cloudy eyes
No
10.darkened color
Yes
11. faded color
No
12. other unusual changes...
Very stresses,Jumping and crashing

Water parameters
1. pH?
7.5
2. Temperature…
90
3. hardness?
200
4. conductivity?
5. TDS?
6. R/O (reverse osmosis) filtered, or Tap (well or chlorinated city water), rain water

7. Water change regime? ( example .. 30 % daily, weekly monthly etc)
Every day 30%
8. appearance (cloudy, green , clear, yellowish etc)
Clean
9. Odor (smells clean or sulfur-lit match smell-anaerobic indicator)
No

Tank parameters
1. Size in gallons/liters?
125G
2. Substrate.? (bare glass, gravel, sand..)
bare glass
3. Planted?
No
4. Drift wood?
No

Filter types
1 Wet/dry?
No
2. Canister?
No
3. hanging box( aquaclear whisper etc)?
No
4. sponges?
Yes
5. supplimental Peat filter?
No
6. supplimental air?
Yes
7. Carbon, resin exchanges, ammo-chips etc
No

General….
1. Diet(what and how often do you feed you fish?
3 times a day
Fozen Blood worm,pellets,beef heart mix
2. Other tank occupants than discus?
No
3. How many Discus in your tank?
20
4. How long have you had them?
3 month
5. Where did you get them (breeder/ Local Fish Shop -LFS)
breeder
6. Tank and filter cleaning schedule?
every day
7. Medications/ salt treatments recently used or tried to treat this problem?
Salt,Malachate green& formalin

[Carol_Roberts]

Do you have other tanks that are OK and this is only one affected? If yes, then something got in the water to show symptoms so fast.

Do you have kids or could anyone have accidently spilled something in the tank?

Did you forget to use the dechlor?

Paint fumes, insecticide, household bleach or ammonia used heavily nearby?

Are they better with water change? (add extra air for high temps)

Carol :heart1:

[Boby]

No. I don’t have kids and I am sure nobody spilled anything in tanks. All other tanks Ok. All my tanks located in one area, so if it were something in the air every tanks would be affected (central air system). I use the same water in all my tanks. Changing 70% of water didn't help. I added malachite green and formaldehyde to the tanks and it looks like they started feel better. I suspect that it can be gills or some other parasite that causes pain (jumping).

[Carol_Roberts]

How would parasites have gotten in tank two months later? Have you added new fish or plants?
Carol :heart1:

[Boby]

Two weeks ago I moved my fish to new 125G tank. They felt great and didn't show any signs of illness. I think that may be changes of environment triggered disease. I still don’t know what happened. Most of them dark in color and refuse to eat. Couple of the fishes feel normal (probably immune). Sick ones don’t have any signs only breathing and stress. I lost 3 of the fish and all of them died like they didn't have enough oxygen.

[Carol_Roberts]

You currently have 20 (3 inch) discus in a 125 bare bottom tank. 10 were moved in two weeks ago after a 4 week quarantine. Now a few are dark,don't eat, stressed, darting, acting like not enough oxygen.

You did a large 70% water change, increased temp to 90 and moved some to a 30 hospital tank and treated with salt and formalin& malachite. Some have died, others showing little or no improvement.

So, if no improvement with formalin try a gram negative anitbiotic like penicillin or kanacyn . . . . anybody else more experience with illness have any ideas?

Carol :heart1: