Help Weird white film on tail of Croaking Gourami - Can't diagnose


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4 years
Hi Everyone,

I have a planted twenty gallon aquarium housing 5 croaking gouramis (Thrichopsis Vittata), 5 otos and 2 mystery snails.
The tank has a sponge filter, DIY CO2, ferts once a week, and 25w heater set to 26 C. The tank receives weekly 50% WC.

Parameters are as follows:
Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate: 20 ppm

Gourami Feeding:
NLS Thera A pellets, frozen brine shrimp, mysis shrimp, and blood worms.

Otos recieve:
Algae from tank, algae pellets, boiled zucchini, cucumber and spinach.

I bought the gouramis as juveniles back in February and quarantined them for 4 weeks, I used General Cure. I initially bought them to
eventually have a pair, but I believe (based on size, colour and finage) that I ended up with a bachelor group. I was considering re-homing
when the virus struck, for the mean time they seem quite content with each-other, no fighting and everyone is eating well.

They have been in my 20 gallon display for 3 months now, and they were all healthy/happy during that time.
However, yesterday during feeding, I noticed an odd white film covering the the tail fin on four of my gouramis.
Only one gourami doesn't have it. I initially freaked out and thought they may have contracted Columinaris somehow, but the film isn't cotton-like and
isn't on their mouth or anywhere else. The otos aren't affected at all, and don't have the film anywhere on their bodies.
All four gouramis are still eating, swimming, and seem otherwise healthy. They don't seem to show any other symptoms besides the film.

Could this be an external parasite or worm that the general cure missed, and took this long to manifest?
This fish don't seem affected by it for now, but it is an unwelcome enigma that I would like gone.

Any ideas or advice anybody has would be greatly appreciated. I have included three photos and circled the effected fish in red.

Thank you in advance.



New Member
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Look up fin and tail rot if their tails look kimd of "ate up". Cotton wool also covers the fish body (eventually).

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