Fin problems?

Hi there! A couple months ago I set up a 30L (roughly 8 gallon) Walstad-style tank for my short-fin betta Jellybean. The tank has no filter but is very heavily planted, and I have been keeping a close eye on the water parameters since this is the first tank of this style I have attempted. Everything has been going great except just yesterday I noticed that Jellybean has a few chunks missing out of her tail and pectoral and dorsal fins. She had the chunk missing from her tail when I bought her, but I’m pretty sure the other missing chunks are new. She is alone in the tank except for some snails (which came ‘free’ with the plants ) and five cherry shrimp which were added to the tank about a week ago. I tested the water today and everything seems okay (0 ammonia, 0 nitrites, 0 nitrates).

I have attached some photos of Jellybean from the day I bought her and from today so you can see what I’m talking about.

When I bought her:


Today:



I’m concerned that she might be either biting her fins or suffering from fin rot, but I don’t have much experience with either condition so I’m not sure. What do you think? Is this something to be concerned about? If so, what should I do? Any advice would be much appreciated.

Thanks in advance!

My gudgeons sometimes get little cuts like that and stuff on their fins. Keep a close eye on it to make sure it doesn't start to rot away or cause any more damage. It should just heal back over time. Give it a week or so (MAYBE two) for it to heal up fully but if you see any further damage and rotting you should come back to see what to do.
To help it heal faster you can use one to two tablespoons per five gallons of salt with no addictives. It has to be pure salt. API has some that I always have on hand. And there is a salt use guide on here. Maybe I can find it and paste it here. This would be the same treatment used if your fish had fin rot but I don't THINK its fin rot. The salt will just help keep the wound clean.

SALT

You can add rock salt (often sold as aquarium 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.



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, Bettas & 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, fish, plants, shrimp or snails.



After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.



If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.



When you first add salt, add the salt to a small bucket of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes.

Thanks for your advice! I'll treat the water with salt and keep an eye on her fins to make sure they don't get any worse