Backyard Aquaponics
A place to discuss aquaponics

Hi guys, my system is about 2yo. I had 10 SP and 20 rainbow trout fingerlings now down to 19 trout (one found its way into the piping) and all but 2 SP have died over the last 3 days with a white fungal looking growth, cloudy eyes and gaping mouths.

My system is 1800l, amm, ites and ates are all 0.

There are 10 large marron in the tank too.

I noticed small white spots and a white fuzzy type fungus about 5 or 6 days ago and treated with 6kg salt.

I am unsure what the issue is, I have done 75% water change but they got worse.

Any thoughts?

how did you do a 75% water change (1,350 litres)... gradually ?
possible changed water parameters stressed the fish out even more ?

>> My system is 1800l, amm, ites and ates are all 0.
I presume this is now after water change.
as it is winter how were your values prior to the problem occurring.

were the SP there prior to [presume] adding the trout recently ?

Yeah it was gradually, about 25% at a time over about 4 days.

The SP have been there for 2 years and the trout were added at the beginning of this season.

Any ideas on what the infection may be? The trout look ok though they're flashing and have signs of mild ich.

Winter saprolegniosis.

If you go to http://www.dpi.nsw.gov.au/fishing/aquac ... lver-perch you can download the PDF of Diagnosis, Treatment & Prevention of the Diseases of the Australian Freshwater Fish Silver Perch (Bidyanus bidyanus). Page 34 is where the section on fungal diseases starts, and yep, that looks like saprolegniosis. It hits hardest in winter when the water temperature is under 16 degrees C, and usually starts after a decrease in temperature (i.e. a cold front goes through and your system chills down some more).

You've already done pretty much all you can by adding salt - if that was before the water change, put more salt in now to bring the levels back up to 2-5 ppt. The other recommendations in the pdf aren't so easy; I'm guessing you can't heat your water to above 20 degrees C (and your trout might object). Other suggestions include dip bathing surviving fish in formalin (which is seriously dangerous if handled wrongly, if you go this route please be extremely careful!) or adding copper sulfate.

I did some more Googling and saprolegniosis (or saprolegniasis, both spellings show up) does seriously affect trout. http://www.tnfish.org/FishDiseasesParas ... legnia.pdf says that water salted to 15 ppt is lethal to the fungus, so dip bathing all your fish in a separate tank/tub at that level for half an hour (take them out immediately if they start acting weird) and then keeping your water quality as high as possible is probably the safest way to try to knock this on the head.

Good luck!

can you get an IBC or large fish tank or something ?
Best bet may be to get the SP away from the trout and then try and treat them.

Do you have a quarantine tank - may be worth getting one if you are mixing species.
separate tank would be one way to do the treatments as well.


Good reference there Mel.

Thanks heaps guys.

I have a seperate tank but it is currently housing my barra over winter and I cannot risk them contracting the disease.

I did set up a hospital salt bath for two of them when it first started but they did not like it at all and we're nearly dead after a about 5 minutes. They came back to life when returned to the tank but never made it.

Should I despatch the two remaining SP and try to save the trout?

What's your ph like? I used to find in the cold weather if the pH was down the silvers would be more susceptible to issues and deaths.

How distressed do your remaining SP seem? If they're struggling to breathe - 'gasping', maybe up at the surface, gills gaping - then it's in their gills and they're probably done for no matter what you do, in which case killing them humanely is probably the kindest thing you can do for them. If their gills are still unaffected they have a decent chance.

(Darren, I'm pretty sure I found that manual from an old post on here somewhere! Just passing it on. )

Ph is 7.
The SP just look manky and aren't doing much, mostly just chilling on the bottom of the tank, none of the fish are gasping for air.
The SP seem to have lost a lot of colour and are almost a pinky white. Cloudy eyes and furry growth.

Well, lost all my 2yo sp which I'm pretty disappointed with. The trout and marron are doing fine though.

Need to find something that's good in the tank year round, my research shows that sp are the only option in Perth though...

Hiya Mike sorry to hear about the fish, my guess is that the disease was brought in from your trout supplier and that if the Sp's are getting sick then it's only a matter of time before the trout start to show signs. It's always a good idea to put new fish into a salt bath or hospital tank prior to adding to a healthy system.
I have had the same problem with the white fungi growth in the past and it was eliminated by running the system with a salt level of 10ppt for several weeks. This level may have been excessive but it solved my problem. As you know I have two systems and splitting the system was a result of the disease being brought in and my way of combatting this issue.
IMO doing water changes won't do much if anything if the fish are already sick, removing all the fish and salt bathing 10ppt with air for 5 minutes and returning to a highly salted tank 5-6ppt would be more beneficial and doing water changes from there altering the salt content from 5ppt to 2ppt then back to 5ppt weekly.
I have a couple of smaller containers 100-200l if you want to borrow for salt bathing.
Remember not to use any aquarium safe chemicals to treat your fish as they are not for eatable fish.

That's a bummer.

Definitely run with a fairly high salt level for the next several weeks at least, that should gradually get the saprolegniosis spores etc out of your system. If the trout are in good condition they may not be in much danger - it's an opportunistic fungus and hits stressed fish. The SP were vulnerable because winter temperatures are out of their best comfort zone.

If you get more silver perch in Spring, they should be good until next winter, then it might be a good idea to see what you can do to keep the water temperatures as high as possible to keep them happy. I checked out your system thread - are you still running constant flood? If you are, that's good; if you switched to siphons or timed F&D since your last update, switching back to CF at night in winter would help. Otherwise you can try insulating your system as much as possible, anything from putting foam insulation around tanks and growbeds to building a greenhouse. Doesn't have to be fancy, just a plastic tent or hoop house would do a decent amount without lifting your temps high enough to upset the trout.

Hey dudes, well skeggly I think your right.

My trout have started to bit the dust. Lost 5 this morning, 2 more looking sick and floating around, the remaining trout are skitty and erratic.

I'm considering a full tear down and restart.

Let me know your thoughts guys.
Really pissed off right now!

Hi Mel,
Yeah still running CF. I'm not sure what is going on with the trout, no white spots, but the same behaviour as if it were ich.

I'll probably run heavy salt for a few weeks without fish and see how it goes.

Skeggly, keen for some marron? Got a few that'll need a new home mate.

Oh damn! That's a bummer.

The PDF I linked earlier recommends maintaining 2-5 ppt salt indefinitely, and also suggests copper sulfate:

copper (as copper sulfate, CuSO4)
0.1–0.2 mg/L, recommend 0.2 mg/L
initially, then monitor and adjust
free Cu+ ion levels daily to maintain
copper concentrations between
0.1 and 0.2 mg/L until disease
controlled; continuous aeration
during treatment; alkalinity must be
> 50 mg/L. Copper may provide some
degree of prevention if used regularly
up to and throughout the high risk
period of winter.

Might be worth a try?