Harlequin rasbora issues

Barbs, Danios, Rasboras, Sharks, Golfish, Koi.
Post Reply
Caol Ila
Junior Member
Posts: 49
Joined: Wed Aug 28, 2019 21:11 pm
Has liked: 0
Been liked: 0

Harlequin rasbora issues

Post by Caol Ila » Wed Jan 15, 2020 12:48 pm

About four months ago, I picked up some harlequin rasboras from an LFS and immediately upon getting them home and into my 240L tank, noticed that one looked off and appeared to have something that looked like cotton wool disease. I took it straight back to the shop. Others all seemed fine, released into tank, all well, and I wrote it off as a netting injury or dodgy fish. Then in mid-December, I noticed another rasbora with fuzzy white growths on its side. I caught it and put it on a quarantine tank. It was the smallest one and I wondered if it had been injured, perhaps by one of the raphael catfish (I'd just bought a second raphael for the tank). Treated it with anti-fungal stuff and it looked better, so it went back into the main tank. Sadly, it died the next day. A week ago, I found another rasbora with cotton wool-looking stuff on the base of its tail. Meanwhile, all the other species in the tank are absolutely fine, and I have some sensitive fish in there when it comes to water quality, like corys and rummy nose tetras. Water parameters test fine -- ammonia, nitrites, nitrates all at 0, and PH circa 6.6. I do 30-50% water changes every week.

What could be going on that's only affecting rasboras? Could it be just a weak stock of rasboras with some kind of underlying issue? I don't know if it's the right thing, but currently all the rasboras are now in the quarantine tank, being treated with Waterlife myxazin.

User avatar
Junior Member
Posts: 28
Joined: Tue Nov 26, 2019 19:53 pm
Has liked: 15 times
Been liked: 43 times

Re: Harlequin rasbora issues

Post by RedLee » Wed Jan 15, 2020 16:46 pm

I haven't got any answers for you on this but it sounds like what happened to one of my Hets before Christmas.
White fluffy growth around the tail. Sadly, its tail fell off and the fish died.
I didn't treat with anything and from then until now, the other Hets look fine.

Hope you get it sorted. :)

User avatar
Super Mod
Super Mod
Posts: 4639
Joined: Sun Jan 21, 2018 17:02 pm
Location: S. Derbyshire
Has liked: 301 times
Been liked: 252 times

Re: Harlequin rasbora issues

Post by plankton » Thu Jan 16, 2020 8:19 am

Sorry for your losses. :(
It certainly sounds as though they came in with a problem.
That's relatively unusual for harlequins, but I expect it's something to do with how (and where) they are farmed.
What you're doing sounds about right.

User avatar
Posts: 244
Joined: Tue Dec 31, 2019 18:07 pm
Location: Sheerness
Has liked: 129 times
Been liked: 117 times

Re: Harlequin rasbora issues

Post by Martinspuddle » Thu Jan 16, 2020 9:46 am

I remember seeing something on the internet a long time ago about Harlequin Rasboras being found to have cotton growths and the affected fish have rapid breathing. Part of the conclusion was bad husbandry while being in dealers shops, I wasn't surprised to be honest.

All aquarium fish can be effected by this problem though poor hygiene, i.e. dealers not sterilising nets between aquariums and very poor water quality, not the first or last time over the years I have come across dealers who don't change their water from one week to another!

Treatments, I found aquarium salt bath can work well, antifungal treatments or in serious cases specific antibiotic formulations from a veterinarian are effective in treating cotton wool disease.
Keeping tropical fish since 1981 and still learning
I have come to the conclusion over the years that all fish have a serious drink problem! :grin:

User avatar
Pleco Fan
Senior Member
Posts: 353
Joined: Tue Mar 19, 2019 12:17 pm
Location: West Yorkshire
Has liked: 161 times
Been liked: 70 times

Re: Harlequin rasbora issues

Post by Pleco Fan » Thu Jan 16, 2020 17:38 pm

When you are doing your water changes you could always add something like Seachem Prime.

Post Reply