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Hi all,

I have had a problem in my 6ft tank for about 2 months now and I wondered if any of you might be able to advise me please?

I introduced some new fish (weather loach) into my tank and within a week little marks started appearing on my bristlenose plecs. They looked like little gouge/bite marks so we assumed that the new weather loach were a bit naughty and were the cause of the problem. Because it affected a few fish we moved the loach into their own sandy bottomed tank and thought everything would then be fine. It wasn't.

I can only assume that the loach brought something in with them as, over the last 8+ weeks we have still had continuous problems with the bristlenose plecs which begins with faint white marks on their backs which become pink over the next few days. It then becomes a bit like a small crater, spreads over the back and then the plec dies. There is no scratching or pecking that we can see. Fish still eating. Pics attached showing different stages of problem.





I am in the UK. We have tried Myxazin twice, Protozin, Sterazin and put the third and final dose of Octozin (double dose) in yesterday evening. We have also been using Pimafix and Melafix. Water changes have been done between these medications and the correct length of time left between switching. Water parameters are excellent. 15-20% water change done every weekend. Lots of filtration (external and internal) and filters cleaned on rotation. Fed on Hikari wafers, catfish pellets and flake food. Lots of bogwood in there for hiding places. Had plecs for 4+ years and never had anything like this before.

Tank holds plecs, gourami, guppies, cory catfish and tetras. Only the plecs are affected by this skin problem which is strange. Also only between 1 and 3 are affected at any one time. Males or females, different sizes.

It has been mentioned on another forum that this might be a fighting issue between males. There are a few males in the tank, probably too many, but we have had far more in there at once previously. They breed like wildfire and we were taking 30+ plecs to a shop every few months before this happened. Of course we're now stuck as we are 99% sure that it's not a fighting issue (although we can't be sure and are open minded about that) so we can't take possibly infected fish to contaminate their stock.

It's not just males that are affected though. The current ill one is female and it ranges between sizes too. There is no pattern. It's almost like a fungus but it's not raised and you can still clearly see the ridges of it's plates (?) Within a day or two these flat white markings will come off along with some of the top skin to reveal the pinky red fleshy bit underneath. This is one of the reasons we don't think it's fighting. It doesn't seem to be fighting damage until after the white bit has eaten away at the bony plate.

Also, two of the plecs we lost a week or so ago were severely bloated. An albino bristlenose was bloated but also had red bloody (under the skin) blotches all over it but no surface damage and a brown bristlenose was bloated but had no visible damage at all.

Thank you so much for reading and for any help you can offer me and my fishies.

P.S. One of the four new weather loach we have seems to have some problem as he is shedding a slime coat regularly and is hanging out by the filters in the new tank. He has only just got ill though (in the last week). MUST be related to the plec problem, mustn't it?

sounds like a fungus or bacteria. As Barbie alluded too: if you can list more info maybe someone can help you. And if you don't have one already, a quarantine tank should always be at hand, even if its not used often, just for things like this. I would definitely isolate all the infected places you can catch, then you will be able to treat more effectively.

Thanks for your replies. Ok, here goes.

1. Water parameters
a) Temperature range = it has been quite hot here this last week so the temp went up to about 34c but it's usually about 24c
b) pH = I believe it's about 6.9 (we have to use crushed coral to maintain this pH as it is naturally very low in there (no fluctuations though)
c) GH = don't know, sorry
d) KH = again don't know
e)Ammonia, Nitrate, Nitrite, levels = 0, 0, 40 (always been a high Nitrite level in this tank)
f) Water change frequency = 15-20% every weekend using gravel vac. Filters cleaned on rotation

2. Tank set up
a) Size = 6ft tank
b) Substrate = gravel
c) Filtration = large external filter big enough for tank on its own plus undergravel filter and 4 small internal filters for water movement
d) Furnishings = plenty of bogwood, a couple of coconut shells and some plants
e) Other tank mates = along with the bristlenose plecs there are tetra, gourami, 1 common plec, female guppies, a polka dot catfish and corydoras
f) How long has it been set-up? = over 5 years
g) When was the last new fish added? = a week before the problems started
h) Foods used and frequency? = Hikari algae wafers, JMC catfish pellets and flake food every evening and courgette once a week after water change

3. Symptoms / Problem description = white fungus-y flat markings which turn into exposure of flesh then death

4. Action taken (if any) = water changes, different meds used with full course given and correct length of time between switching as well as water changes and "waiting to see what happens"

5. Medications used (if any) = Myxazin, Protozin, Sterazin, Octozin (all by Waterlife) along with Melafix and Pimafix

I'm not sure where I could go for scrapings in the UK, maybe someone could advise with that please? It seems that apart from forums like this you're pretty much on your own unless you have a good fish place nearby that know their stuff! Even then it's pretty limited a lot of the time.

The wounds end up looking like bite marks but they start off like flat fungus-y markings that you can still see the pattern of the bony plates through. It's only after these come off that it ends up like bite marks.

We are trying our hardest to keep a close eye on any affected fish but there are quite a few pieces of bogwood in the tank so they have plenty of hiding places. I suppose it could be that they are getting the white markings on them (some on fins as well and always round (not Ich-like though, much larger)) and other fish are trying to help/can't resist a tasty snack and it's them that are making it all much worse.

I need to find out what I can do about the initial white mark stage to see if I can stop it before it develops but we've tried so much already.

Thanks, Barbie. I might see if we can set up a small quarantine tank this weekend and then remove any fish straightaway that have the white markings on them. This will determine whether other fish are causing the problem to get worse or whether it's part of the "disease". This might help us come to some sort of proper diagnosis.

Will get a big water change done in there and set up another tank and see what happens.

e)Ammonia, Nitrate, Nitrite, levels = 0, 0, 40 (always been a high Nitrite level in this tank)
Are you mixing up your Nitrite and Nitrate readings? 40ppm Nitrate is quite normal here in the uk, but 40ppm Nitrite is really bad.

Sorry, MrR, you're correct. I meant nitrite is 0 and nitrate is 40.

We have now set up a small quarantine tank which is currently holding 3 fish all with the advanced stages of the problem.

There are a couple of plecs with the first stage (small white markings) in the 6ft tank which we keep trying to catch but they are very quick on their fins so 6ft tank gets destroyed and no sign of fishy each time we try! haha Will keep trying though.

We thought if we could isolate the fish as soon as they show signs we might find out whether it's pecking from other fish that is making the whole thing worse and we're just suffering from some nasty fungus.

Going to do a 50% water change this weekend and we are seriously thinking about stripping the 6ft tank to get the undergravel filter out. We are starting to wonder whether there is something in there that is bad (had to do this a few years ago too as the undergravel started causing problems. Do *not* know why we put another one in).

Also, the sick weather loach that we think started this problem died yesterday. Slime coat peeling badly, black face.

Back when I used under gravel filters regularly, I made it a habit to tear them down once a year as there is always detritus buildup with these systems. Very good idea.

The loach was producing mucus as a response to the disease (not necessarily the disease your plecos are dealing with now).

I'm worried about removing the undergravel filter as I think it's probably pretty bad under there. It's small sections that clip together - would you advise a full strip down or just shuffle everyone along?