Backyard Aquaponics
A place to discuss aquaponics

Hello all!

Just recently (maybe 10 days ago) had our first fish casualties. Two dead silver perch.

Water quality is good - the only thing I've done different recently is adding a little iron chelate, Epsom salts and power feed to correct nutrient deficiencies in my plants.

I kept checking water quality though and Ammonia, Nitrites and Nitrates all were undetectable.

No other fish have died in the 10 days (I feed & check fish daily)

Here's a photo of the dead fish:



They seem to be stuck together with a kind of hairy fungus that I've also noticed on any ineaten fish food left floating on top of the water.

I assume the fungus colonized the fish post mortem...

But just wondering if I need to worry?

If you've got similar looking white fluffy stuff growing on uneaten fish then in all likelihood it's saprolegnia.

What is the water temp and pH?... Are you running any salt in the system?

Eck! Er... maybe?

If there's time for fungus to grow on uneaten food before you see/remove it, it's hanging around longer than it should - and it means there's a lot of fungus spores in your water. Do any of your other fish have visible pale spots, even if they don't look fuzzy? Are any of them swimming oddly, or seeming to have trouble breathing?

http://www.dpi.nsw.gov.au/fishing/aquac ... lver-perch - there's a free PDF you can download there, Diagnosis, Treatment & Prevention of the Diseases of the Australian Freshwater Fish Silver Perch (Bidyanus bidyanus). Page 34, look up saprolegniosis. It hits worst when your water temperature is under 16 degrees (and at this time of year, I bet it is).

I'd cut back on how much you're feeding until you're sure the fish are cleaning it all up in 5 minutes. Any time you see uneaten food floating around after that, net it out right away. Also, salt your system to 1-3 ppt if it isn't already, and keep it that way at least until things warm up and your water temperature is up out of the danger zone.

Fingers crossed and good luck!

Thanks for your help.

I have pool salt - how much should I add to my system?

Approx 4,000 - 4,500L

people usually run systems at 1-2ppt.

1kg salt per 1000l = 1ppt.

Ok so I just added 10 cups of salt which at 250gms per cup roughly equates to 2.5kg

Had to fish out 5 more dead fish - in the other tank this time.

Takes my death tally to 7

Will test the water parameters now

Water temp is 14.7

A mate had a run of this (saprolegnia) recently we stuck all the fish in a makeshift hospital system salted to 3ppt and didn't lose another fish .

Its one of the hardest things about AP ive had to get my head around is DONT FEED when the water is to cold its just too risky .

The fungus breeds up on organic matter

Your going to need lots more salt

I just added another 20 cups. So in total have added 7.5kg of pool salt to the system.

I know getting the fish out and into a hospital tank is the best option but...

I've got insane work hours all week then I'm leaving hubby alone with the animals for 2 weeks while I take the kids OS to visit Granny...

The earliest I could set up the hospital tank is Thursday and I'm not confident my husband could keep them alive in the hospital tank

I have scooped up as much uneaten food as I could see

There wasn't much as I have only been feeding the fish 1tsp daily during winter

I know it's always in my small system, I've seen it on uneaten pellets often enough in the ST, but it hasn't affected the fish, although there is always about 1ppm salinity

I am shore you will find power feed is your problem just straight seasol is ok
Power feed will give a big hit of ammonia by the time you tested it it will have dispersed

You could be onto something....

The tank where I found the 5 new dead fish was just a few days after I added a dose of power feed directly to the FT rather than putting it in the grow bed as I have previously done....

Yeah. Whether the fish are dying of saprolegniosis, or dying and then being colonised by saprolegniosis, the powerfeed is probably the proximate cause. It'd cause a big ammonia spike, then a nitrite spike, either of which could kill fish, and even if it didn't kill them outright it would stress and weaken them... and saprolegniosis hits hardest when it's cold (it is), when water quality is low (spikes count), and when fish are stressed/weakened.

It's a bummer to lose fish but at least now you know what's up?

if you need to do that again, spray it onto the plants, dont add it to the tanks / growbeds, but dont make it strong.

Better still don't use power feed ever