Betta showing signs of fin rot in a community tank—now what?

[AmyFromDE]

Hi all. I'm going to try this platform because I keep finding conflicting information in my Google searches. Fingers crossed. 

Back in the fall, I somehow knocked the tank out cycle and had an ammonia spike. Took me a few weeks to get it back to stable and thankfully I only lost a few fish (two tetras and a snail) and not the whole tank. But, what a complete nightmare! I have a 20 gallon tank. It's a happy community of five tetras, a gourami, a bristlenose, two dwarf frogs, two albino corys, a betta, and two snails. All seem to be well now except Dijon, my mustard Betta. Looks like he's now battling fin rot? Yay, me. (Sarcasm)

His signs seem pretty consistent with fin rot/fungal infection. This past week he's been pretty inactive. Hanging out in his floating log (lounging really, to one side) or in the tunnel on the bottom. Yes, I know bettas are lazy and like to lounge, but he's normally more active. And, today I noticed that his tail looks a little less, a little shorter if you will. The edges are always sorta frayed so I'm not great at judging by that, but I'm 98% sure he had more tail a week ago. 

I'm pretty anal about changing 40% of the water each week and checking levels. Especially after knocking the whole system out of whack a few months ago. The only thing I think of that would have caused his immune system to drop, allowing for fin rot, is that situation in the fall. Regardless, I'd like to help him and I'm not sure what more I can do with snails in the tank to treat him besides water changes. Any suggestions? I don't have a setup for another tank, so I'm scared to use KanaPlex. 

Help me save Dijon! He's a peaceful betta and only a year and half old.   

[Squeegee79]

Couple of questions. 

1. What are the water parameters specifically.

2. What kind of Gourami?

3. Do you have any pictures of it?

[AmyFromDE]

PH 7 • Ammonia 0 • Nitrate 0 • Nitrite 0 

Blue dwarf Gourami 

This is Dijon looking his fishy finest. (Ok, maybe not his finest)

[Colu]

You could Quarantine and treat with aquarium salt 1 table spoon for 3gallons if it get worse try maracyn or maracyn2 your gourami's could nipping the fins of your betta

[Squeegee79]

I don't really see any infection from what I can see in the pics. The dwarf gourami and the skirt tetra could definitely be picking at him though. Colu's salt recommendation should do the trick...may want to get him his own tank though as they likely won't stop picking the fins.