Sick or Injured Danio

[whiddett]

Hi. I have a 260 litre tank which I started on 15 May. It currently contains 3 leopard danios, 2 white cloud mountain minows, 2 denison barbs, a Leopard catfish and a Pim Pictus catfish. I went away on Thursday and just came back today to find something wrong with 1 of the Danios. He is hanging around fairly stationary near the surface of the water and has what looks like a fairly big blister on the side of his body. The blister/lump has some blood in it and is open in the centre. It looks almost like a bite but I doubt very much that one of the other fish has bitten him. Can anyone tell me what this might be and what I should do?
Thanks
Steve

[Zagz]

Since the tank is so new, have you tested the water parameters since you are back? I would first do a water change and then add some melafix to the tank. Keep the water clean and add the melafix as needed. It may be an injury from another fish or an ornament or a bacterial infection. Try the melafix for a couple of days and see if he improves.

[whiddett]

Yes I have been testing my water since 11 June when I first got my API master test kit. The results seem a little odd to me though. The first set of results were PH 8, Ammonia 1ppm, Nitrite 0, Nitrate 10ppm. I then added some seed material from my old tank as I was concerned about the ammonia and wanted to speed up the cycle. 2 days later the ammonia had dropped to around 0.5ppm. Everything else stayed the same. I was then away for 10 days and tested again on 24 June and found nothing had changed again. The ammonia had possibly dropped from the high side of 0.5ppm to the low side of 0.5ppm. I've then tested again today and got PH 8, Ammonia 1ppm, Nitrite 0, Nitrate 10ppm again. It seems odd to me that I am yet to see any Nitrites or increase in Nitrates. Is this normal?
I dont have any meds available to hand and wont be able to get any until tomorrow. If I leave him in the tank am I putting my other fish at risk? Im afraid I dont have a quarantine tank.

[whiddett]

I noticed the Danio was developing a similar lump on the other side of his body and didnt seem at all happy so decided that in the lack of advice as to what this could be I would euthanase him. I would really like to know what the problem was though uncase it recurs in any of the other fish. The Denison Barbs and Pim Pictus are my favourites so I'd hate to lose them. Any ideas anyone?

[meegosh]

I'd agree with Anne on this one, its either a bite, scratches from decor, or a bacterial infection. If it developed on both sides of the fish I would lean more towards the infection. I'm sure you already have but I would do some large water changes just to be on the safe side.

Sorry for your loss!