Help with white spots (not ich) on cory fins

[Yaya16]

Hi all

New cory breeder and member. I have about 25, 200 liter aquariums and three 500 liter plastic tanks. I have been keeping several cory spp. for about three months. Some of the fish have a white growth on their fins and not on any other body part. The growth is rather large white usually round but sometimes goes along the fin appearing on the caudal or dorsal fins mostly.

I see no clear signs of difference in behavior. I should mention that the pH is around 8.2! but the water is soft (see below) I was able to breed some of the spp. sporadically. Also, I feed bloodworms almost daily (together with dry feed and some artemia) and I cycled the tanks with some of the fish. The phenomenon is spreading slowly to other fish and other tanks and so far is non lethal. Any idea what this is? Would appreciate your advice on identification and treatment.Please see all information below:

Species and status:
Aeneus bronze and albino - infected
Venezuelanus- infected
Simulatus- infected
Panda- not infected
Septentrionalis- not infected
Paleatus- not infected

Water parameters:
Temp range: 23-26 deg C
pH: 8.2!!
Gh: 6 Deg. German
KH: 5 Deg. German
Ammonia, nitrite are 0 and nitrate is low around 10 ppm, 40% - 50% water changes were made very frequently at first daily for the first week and the every two days in the 2nd and 3rd now once a week. No chemicals were used.

Tanks are 200 liters some are divided by a screen into 100 l tanks, no substrate, sponge filter and air stone, no heater (temp is regulated with AC), java moss in some of the tanks. Tanks are starting to get brown algae in them as happens after cycling. Tanks have been running with fish for about three months. I have moved and added a lot of fish around about a month ago but have seen this on a few fish before the big change was made (I had only bronze and albino at the time)

I recently tried to treat with directly applying methylene blue to the affected areas, possibly there is some if not major improvement.

Any advice will be greatly appreciated.

Thank you

[Yaya16]

Edit: after another careful look I see that some of the fish have damaged fins (fin rot?) maybe a secondary thing? I am adding some photos. Please send your comments. Thank you

[bekateen]

Hi Yaya16,

I've seen that many times and it's always water quality related. The heavy feeding schedule is to blame, and the algae growth is a clue (algae grows fastest with excess light and nutrients).

I'm not great with meds, but I would do big (80-90%) water changes then treat with something like Paraguard.

Good luck,
Eric

[Yaya16]

Thanks Eric, I am doing a full clean i.e big water change, filter clean and scrubbing the tank. See how this goes. Cheers