I know there is probably thousands of posts on this subject.
I first noticed one of guppies had abit of 'nip' in his tail, he's got quite a big, but not very colourful tail. It had some red swelling around it, which comes and goes. I thought it was weird since there has been little aggression amongst my guppies since I got them. I have a 45 litre tank, heavily planted, with 15 guppies. all males. Anyway, being a new and worried owner I rushed to get some medicine and toxin salt (general medicine, which treat fin rot, ulcer etc.) It was then I started noticing some of my other guppies weren't looking too good either. I knew one or two had split tail (I bought them that way but was told they would heal pretty soon -they were pretty anyway-)
What I am really confused is there is a varying degree of damage amongst my guppies. The first group of 4 I got - Tut had a split tail, Churchill, Napoleon and Gandhi were fine. Napoleon now has a healing ragged tail, and Churchill a small split. My second group - Dickens was fine, but has some slight damage at the tip of his tail. Columbus is completely find. Oscar Wilde and Richard lion heart (both have the largest tails) are now showing signs of ragged tails. My third group were all endlers, Leonidas, Aristotle, Darwin and Van Gogh, they are all fine. and my last group, Mandela, Picasso and Marx were all fine, and Xerxes tail was already ragged and split. I am noticing the guppies with the longest, or biggest tails seem to be hit first.
I've had the water tests in stores and everything is fine, Ph abit high, but that will go with water changes. I think I know what has caused this though. when I feed my guppies I give them flakes, but a crush them up into pieces (thinking so the fish will all get some, and it's easier for them to eat) I was told this actually causes a lot of waste food and harmful bacteria. Which would explain why my separate betta tank is doing so well, I only give him two three small pellets and he eats them all.
now it' been 5 day since I added the medicine (once per day as instructed) and changed the water (25% with treated water), and I have noticed some positive result. one guppy with a really ragged tail has started to heal (Napoleon). But I still have noticed some guppies with more split tail (as opposed to ragged) have not healed yet. One is Tut, one of the first four guppies I got when I started my tank (almost a month ago) and the most recent, Xerxes (Whom I got almost a week or so ago - but he's got a split and slightly ragged tail). Also Richard Lionheart and Oscar Wilde (With the biggest tails) are still looking abit frayed at the edges.
These splits aren't right down to the end of the tail, so I can't see why they haven't healed. how long do these things take ? am I just expecting too much too soon ? All are still eating and swimming fine.