Possible fin rot and something else on scales?

[Tefloncat]

I have 100 gallon tank with 30 gallon sump. I have Smart AWC Touch which does an auto 5 gallon water change every 2 hours from a 55 gallon autofill double RO filtration. In the tank I have 5 adults and 7 babies from 2 different pairs (they need like rabbits). My problem is in the last month fin rot has reared its ugly head. I might be feeding to much blood worms (1 lb. last roughly 3-4 weeks, this also includes feeding 2 very large breeding pair in a separate tank). A problem could be 1)they will only eat blood worms 2) only if you hold the frozen piece (yea, they're kind of spoiled) 3) my son loves holding them (in the water
), they appear to love it equally as they will only let him do this. He doesn't wash his hands prior, even though I tell him he can affect their slime coat and pass on potentially dangerous bacteria.
How do I treat them?
Parameters
Temperature 86⁰f
pH 6.6
NH³/NH⁴ 0ppm
NO² 0ppm
NO3 0ppm roughly 5-10ppm
KH 3 drops
GH 3 drops
Additional fish in this tank
1 queen arabesque pleco
2 stardust plecos
15 cardinal tetras
6 various dwarf cichlids
10 various non reproducing snails
Thanks
Eric

[smsimcik]

Fin rot is caused by poor water quality and stress. Even though you are doing auto water changes and your nitrates are not too bad, there are probably higher than normal DOCs and bacteria in the water column from over feeding. I also think your tank is a little overstocked. You don't say if you have substate or if you're bare bottom. If you have substrate, that will make the problem worse. You probably need to be doing larger water changes, 70-80% daily for a while along with vacuuming the substrate if you have substrate. Also, why are you using RO water to do your auto refill? RO water isn't necessary. Is something wrong with your tap water?

Feeding only bloodworms is a big problem. They do not have much nutrition on their own. Your fish are probably suffering from some nutritional deficiencies that prevents them from having healthy immune systems to fight off something like fin rot. They need to be eating a high quality flake or pellet food with only occasional blood worms. If you can find freeze dried blackworms, they are much more nutritious than bloodworms.

If you want to treat the affected fish, they need to be taken out of the display tank and treated in a hospital tank with something like Furan or erythromycin. They will probably heal eventually with antibiotics and better water quality.

[dspeers]

In general, I think your water change regimen, 60 gallons/24 hours is sufficient (as demonstrated by your NO3 level), BUT using any frozen food every day, albeit blood worms or beef heart adds more of a bioload to the water column and promotes higher consequent bacterial growth. Bigger issue is the nutritionally deficient diet of blood worms only. Options for reducing the bacterial count include: change diet, change more water, and/or add UV at sterilizer levels. That's one reason why folks growing out juveniles change more than 50% per day.
Very much endorse a hospital tank to treat affected fish, but you have to change something in the DT or you will have recurrent problems.
I Don't get your water parameters, double RO filter but gH and kH 3 degrees, that seems contradictory or time for new cartridge, are you mixing in some tap? Also why RO at all? are your discus wild caught? Did you ask your source what water they use? Also not quite sure what NO3 0ppm roughly 5-10ppm means? Need to be a tad more draconian with son, thorough hand washing does more than reduce bacteria, keeps all of the crud (seen and unseen) hands accumulate from being rinsed off in the tank, should be an absolute requirement. Also title implies you are not fully sure of Dx, pictures?