Backyard Aquaponics
A place to discuss aquaponics

Had a strange two days with the fish - not eating, and being very shy (not in their usual happy-to-see-us spot)

This morning we have six deaths, three floating, two on the bottom, and one simmig around upside down, who 10 minutes later was dead on the bottom. Top of the water has a disgustng oily sheen (now dissipating). Here are the test results:

pH = 7.5
Ammonia = 0.25
Nitrite <0.05
Nitrate = 5
O2 = 7 (usually sits at about 15)
T = 18C

The factors in the mix are:
- trauma from taking two out and weighing them
- temperature (we had a problem yesterday and the T went up to 21C
- oxygen levels (bubbler appears to still be working, pump has been running) Have just cleaned the airstones - three of which were dirty
- low water level in the sump meaning that less water has been circulating (i.e. pump is less efficient)
- I have seen a couple of tiny little red "worms" in the water today - parasites?

Any suggestions? would be keen to not lose the next 95 !

I am guessing temperature spike to 21 and the lower O2 levels have conspired to get you. Get more air in there quickly would be what I would do.

Andrew
As someone on this site said to us when it happened to us " Rite of passage".

Oily sheen on the water maybe from the fish food. We cut back on feed when the temperature goes over 18C as the fish do not seem to be hungry and the food sinks to the bottom and starts messing the water up.

Start thinking of getting trout out of the polytunnel in the warm weather as it will be too hot for trout and the consequent low oxygen holding property of the water will be insufficient for them.

What we do when things start going pear shaped is to flush,flush flush. This will sort out ammonia etc but won't sort out the temperature and that is the one you are going to have to decide upon. As you suggested in the other post, think alternatives carp,tilapia,sturgeon,blue whale anything that will tolerate the temperature in the polytunnel. Forget the blue whale- no market for them without 10 ton of chips.

Just a thought, high temps cause them stress so pulling them out of the tank for a body check may not be the way forward.

WD and OH.

The temp is now back to about 18, and they've previously been happy in the 18-20 range. Have just put a new, huge, air pump into the tank - so big we're getting waves. Will see if that work - have lost another two during the shopping trip.

No deaths in the last two hours! The new air pump and stones are much more effective than the last - 10x50mm airstones seem to be doing a far better job than the 6x120mm stones than I had in there before.
O2 level back above 15. Now the fish have to swim against the force of the new airpump!

We have lost some more . . total now up to 13. the rest seem to be trying to hide behind the pipes to keep out of the tsunami that the new airpump is causing. I thought Trout we supposed to like a bit of flow!

I think adding some salt might help with the stressed fish... 1ppt perhaps??

Trout like a bit of flow but constant buffeting from too much air could be tiring them out a bit which might not help the ones who were weak.

How big are they, any worth harvesting? Of course you don't want to go stressing them by netting them if they are definitely not big enough.

I'll try the salt (I seem to remember that pool salt is the thing to try?)

They largest fish is only 50g - not really worth harvesting, although I'm not sure how to dispose of the dead ones so maybe we should just fry them up.

oh these poor Welsh AP'ers
"my water temps gone up to 21"
get some W.A. trout that can handle 30 degrees like mine did ( till I et them ) hehehehe

DO doesnt present itself 2 days before it happens, I'd be looking for something toxic leeching into the system , like metals :

"This morning we have six deaths, three floating, two on the bottom, and one simmig around upside down, who 10 minutes later was dead on the bottom"

sounds like Exactly what happened to me a few weeks ago when the metal on an IBC frame started to seriously rust and fall into the water - zinc , ali, whatever else = dead fish swimming around upside down first then dropping dead

I killed half my sick fish, and cured half my sick fish, by doing a pretty huge water change with much higher pH water ( bore water ) over about an hour

That's 21C in a Polytunnel too doubt we'd get over 15 outside.

OK, have just added 2kg of Dishwasher Salt (not many pool shops in Manchester) to the fishtank (approx 2500L) so just under 1ppt by my calcs. Have got more I can add too - is it safer to be 1.5 than 0.6ppt?

No sign of any metal in the system.

I can make you a metal sign if you want ( it will say "no metals in system")...

mine did the same thing
I suspected metal or some tort of toxin, so I salted ( fish swimming around, upside down etc )

the more salt I added, the more fish died. pH change (up) seemed to help, salt seemd to kill. I know this is completely opposite to what usually works but thats what I found when my fish were doing what it sounds like your fish are doing

as soon as I isolated the section that had possible metal leaking into it and did (another) water change - no more deaths

OK, 20 dead so far plus one on her back gasping.

A large number of the casualties have come out with either wide open, or very swollen, gills. Presumably a sign of lack of oxygen?

--------------

Just had another thought - no metals in the system, but the lid over the fishtank is treated (Tanalised?) timber, and I've noticed today that it has been getting splashed by the inlet. Could something be leaching from that into the tank?

Only four dead overnight, so we might be past the worst (Or I just can't see them all dead under the plumbing at the bottom)

Have salted the whole system now - 4kg Dishwasher salt to about 5,000 litres ish. Should I add more?

We're off out today so that'll save me from the drip-feeding of casualties that I had yesterday - will just have to see how many are belly-up tonight.

Not so sure about "dishwasher salt".... try and use pure "sea salt"....

A lot of other salts may contain additives, and/or anti-caking agents...