Betta Head Ulcer??

[kate64]

Hi everyone, it seems I cannot get away from the Betta issues! When I went to feed tonight I noticed that one of the two female bettas in my 20g tank has an ulceration on her head. Or at least that is what it looks like. I'm not sure if it is an injury or a disease but I have attached pictured so hopefully someone more knowledgable may be able to tell. I watch this tank closely -- I know aggression can arise between 2 female bettas -- however I have yet to see any and they have been together for 3 weeks. They seem to ignore each other 75% of the time and swim together the rest of the time (slow and calm swimming - I have yet to see chasing, nipping, or anything). They have guppies (4 adult females, 1 adult male endler, several juveniles and even more fry -- which I plan to drop off at the store), some ghost shrimp, snails, and a siamese algae eater as tank mates. The only other fish in the tank who looks unhealthy is a female guppy -- but she looks more old and hunchbacked than actually sick. When I first added the currently affected Betta, I had actually added her with a different betta than the one she is currently with. That betta ended up getting very ill and dying shortly after purchasing her despite medicating the tank with general cure and then separating her into isolation and medicating her with antibiotics separately. I'm not sure if the problems are related? That Betta seemed to have a different issue but who am I to say for sure. Current Betta tank mate however (the one she has been with for 3 weeks) is completely healthy. Both fish are active and a little fat from preying on some of the newborn guppy fry. Water parameters are good - I test every week before the water change (liquid for ammonia and pH, strips for nitrites and nitrates) and it is consistently 7.2 pH, 0/0/<20ppm for ammonia, nitrites and nitrates respectively by the end of each week -- as it was this past Friday too. The tank is pretty densely planted and I do 25% water changes weekly. I do have hornwort -- could she have injured herself on it? Last water change was Friday night. Tank is cycled and has been running for 5 months and is equipped with a sponge filter as well as a marineland biowheel filter and a 100w heater currently set at 82 (I was told to set @82 for these fish by LFS - but I can easily lower the temp if anyone thinks it is to high). I dose phosphorus every few weeks (per research about green spot algae), and flourish at every water change as well as excel @1/2 dose 2x per week (in hopes of getting my dwarf hairgrass to grow into a carpet!). The tank is fed bug bites spirulena flakes, tetra min tropical flakes and omega one betta pellets. I only recently added the bug bites into the mix for some variety. Only other change is I added some boiled egg shell this weekend (per advice from LFS when I mentioned my nerite snail had developed some odd ridges in his shell). Thanks in advance for your help! All pictures are from this evening. I'd really appreciate advice per if this is something I should really worry about, isolate and treat or if I should just monitor closely?

 

[Barry Tetra]

Try 75% water change, substrate clean and add salt (dissoved it before adding it)