Need help identifying disease on Discus

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Tank size: 160 gal (130 display tank + 30 gal sump)
pH: 6.94
ammonia: 0
nitrite: 0
nitrate: <10
kH: 2.5
gH: 2.5
tank temp: 87

Fish Symptoms (include full description including lesion, color, location, fish behavior):
- Fungus-like growth on root of pectoral fins
- Fish hiding, but still eating

Volume and Frequency of water changes:
- 25% every 2nd day

Chemical Additives or Media in your tank:
- Normally run carbon + purigen, but removed it to start medicating tank
- Medicated with Polyguard and Stressguard
- Added Seed as a precaution to support Biofilter

Tank inhabitants:
- 12x Discus (various size ... ranging from 1.5" to 5")
- 5x Neon Tetra
- 2x German Blue Ram
- 5x Cory Cat
- 2x Siamese Algae Eater
- 4x Hoarsehead Loach

Recent additions to your tank (living or decoration):
- None

Exposure to chemicals:
- None (other than recent addition of Polyguard and Stressgaurd to treat symptoms)

Digital photo (include if possible):
- See attached

Hi and welcome to the forum

Can you post a couple more pictures, make them a bit bigger if possible, but not too big?

How long has the tank been set up for?
Do you gravel clean the substrate when you do a water change?
When was the last time you cleaned the filter?
How often do you clean the filter?
How do you clean the filter?

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If you haven't cleaned the filter in the last 2 weeks, then clean it.
Power filters should be cleaned at least once a month and every 2 weeks is better. Wash filter media/ materials in a bucket of tank water.

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You should do bigger water changes. Make sure you dechlorinate any new water before it's added to the tank.

You do water changes for 2 main reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.

Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.

If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.

Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and makes the environment cleaner and healthier for the fish.

The blue coloured discus appears to have a fungal infection on the pectoral fin.
Methylene blue works well on most fungal infections but can stain the silicon blue and kill filter bacteria.
Triple/ Tri sulpha usually works too and shouldn't wipe out the filter bacteria.


You can try salt to treat fungal infections.
You can add rock salt (often sold as aquarium salt), sea salt or swimming pool salt to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.

If you only have livebearers (guppies, platies, swordtails, mollies), goldfish or rainbowfish in the tank you can double that dose rate, so you would add 2 heaped tablespoons per 20 litres and if there is no improvement after 48 hours, then increase it so there is a total of 4 heaped tablespoons of salt per 20 litres.

Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.

The salt will not affect the beneficial filter bacteria but the higher dose rate will affect some plants. The lower dose rate will not affect plants.

After you use salt and the fish have recovered, you do a 10% water change each day for a week. Then do a 20% water change each day for a week. Then you can do bigger water changes after that.

If you do water changes while using salt, you should add salt to the new water before it's added to the tank.

Hello, and welcome to the forum!

It seems your fish have an illness called “fungus”, a fungus that grows on the outside of the fish. I recommend treating it like @Colin_T said. He is very knowledgeable in everything fish related, so he shouldn’t tent you down! Good luck!

(Please enter the July TOTM contest, by clicking the banner at the top of your screen, thank you!)

With respect to your questions:

How long has the tank been set up for? - 18 MONTHS
Do you gravel clean the substrate when you do a water change? - YES
When was the last time you cleaned the filter? - YESTERDAY
How often do you clean the filter? - EVERY THREE (3) DAYS
How do you clean the filter? - REPLACE THE FILTER SOCKS (2x 7", 100 micron fleece filter socks in sump ... I just throw them away and replace them with new ones)

As requested, here's a bigger picture:

Is that the same fish in both pictures?
In the first picture, the base of the pectoral fin is blue. In the second pic it is red. If this is correct, the base of the fin has been damaged and appears to have a bacterial infection. However, the white bits in the fin looks more like a calcium growth in the fin rays rather than a fungal infection.

How long has it had the white bits on the fin?

Methylene Blue, Triple Sulpha and salt will all treat minor bacterial infections too, so you can try those. If you have a smaller hospital tank, it will require less medication than treating the main tank.

You can keep using the PolyGuard instead of the things I mention and see how it goes with them. However, I have never used them so can't comment on whether or not it will help.