Backyard Aquaponics
A place to discuss aquaponics

I've gone from 60 trout fingerlings to 15 in three weeks

Ph is 7. Ammonia and Nitrite are zero. Water is clear.

Oxygen is provided via inlet from growbeds (via sump - splashes in there) splashing in to the fish tank. I also put a pump in the fish tank for more splashing via a T-piece (so just circulating within the tank). I also have an air pump going.

Have added lots of salt.

They started happy enough but won't eat now and spend all day at the surface clustered near the water inlets.

I thought heat might be an issue. On a 30 degree day the water temp got to 24 degrees. I added ice and turned the pump (from growbeds/sump) off during the middle of the day. Was a lot cooler the last couple of days but still losing trout at an alarming rate.

So disappointing... I might be down to zero trout by the weekend.

What else can I do?

Sorry to hear about your fish.

Edit: I suggested adding more oxygen but looking back at your post you already did. Them hanging out by the inflow makes me wonder about the air still. If the tank is getting any sunlight I'd block that.

Sorry about your trout,its tough to lose fish especially that many. Could be you got your fingerlings too early, there is only so much oxygen that can be dissolved into warm water. If they came from a Snowy Mountains hatchery,they were born and bred into richly oxygenated 12 degree or less water so I would do anything I could to lower the temperature. Cover the tank and growbeds, put a nozzle on that second pump and spray water into the fish tank from above while running a fan over it, constant flood during the day then flood and drain if it cools down at night . Good luck I hope you can save the last few.

Thank you both. I will try to cover the tank more and try to improve the spray / cooling

I'd suspect 24C water, or a large diurnal temp range, may be the problem, if they are from a cold water hatchery. Even so, if it is at saturation and they've had a bit of time to acclimatise, there should be enough dissolved O2 for them to survive.

How much water is there in your system? What is the water temp first thing in the morning and in the late afternoon on a hot day?

I'm still waiting for it to cool down some more before getting my trout- 35 and 36C forecast for the next 2 days.

G'day mate, where you a part of the recent group buy in Canberra?

I only mention it because I picked up my order of 16 - they went ok for the first period but we had that week of warm weather and my water temps were 24 aswell and I'm now down to about 5 fish and they look like they'll kick the bucket too.

The fish went from swimming happily under the grow bed darkness and were eating well (despite water temps a being at 24 for a few days so I'd been concerned and trying to cool the water) then one day noticed they went off the feed and then the deaths began lost nearly half that one day alone and have lost a few each day since. The remaining few are now barely swimming (constantly hanging about the surface) , still not eating and generally doing poorly.

The bigger ones were (mostly) the first to die.

From what little knowledge I have with trout and AP in general I believe they'll all die due to exposure to the extended high water temps as the damage has been done (??).... Hopefully that's not the case for you but I suspect we are falling victim to the same issues....

For the record I have 1000 litres, constant flood and drain, system is under a carport and semi protected. I tried in vain to cool the water... The fish otherwise looked healthy as far as I can tell.

pH 7.0-7.5
Am 0
Ni 0
Na 0
Measured at least a week at 24 degrees water temps.... Way too high as we all know... Despite good aeration.

I don't know if anyone else in the group buy has suffered but I'm guessing it's likely.... Perhaps it was a little soon to order them and I might try and get some more come mid-late March pending weather....


Hope things improve for you and if you find a root cause let me know.

Happens every year unfortunately.

It's about now and for the next couple is months people stock too early or overstock. Either way it doesn't end well if your system and/or temps are not ideal.

You won't be the first.

Hey. Yep I got them through the group buy. Sounds like we've had a similar experience.

You're probably right (hopefully not though!) about the damage being done already. Fingers crossed.

They are in a full IBC. They were partially split across two tanks originally but moved them into one as numbers dwindled.

Likewise I will see where I'm at mid to late March and whether to try to buy some more.

Temperature wise I think it's maxing out around 19 degrees now when it's warmer after I made adjustments. Overnight temps should be a fair few degrees lower.

You must be right about the damage done and only a matter of time until they all go Cunningstunter. Lost another 5 overnight and that's probably been the coolest temp so far. Water was 17 degrees this morning.

A drop of 8C or more in water temperature overnight can be a problem for many fish too, and an exposed IBC can lose and gain quite a bit of heat each day.

I wish I was wrong I really do but I recall seeing some information that if trout (and I'm guessing many species of fish) are subjected to high water temps/lower DO levels that it damages their gills and it's pretty well game over
Again I hope I'm mistaken but judging by both of our experiences so far it seems to be the case.

My water temps have also been between 17-19 last few days but I continue to lose them.....the ones that are left are still not eating and sitting on the surface.

I really just think the group order was arranged too early - no one's fault certainly as summer has been pretty mild so it could've gone either way. Question being I wonder.... is how many others in the group buy have suffered. I'll flick you a PM shortly.

If they are hatched at a very constant water temperature the swing from day to night temp is stressing them. If your oxygen is ok I would guess they die from a secondary issues due to stress. You mentioned they ride the surface. Are their gill plates moving rapidly?
They should not die that long after being exposed to low oxygen/high temp.
Would help if you post a photo of the most recent mort. Incl a shot of the gills.
When you say lots of salt, how much is that?
Hope you get a few through.
Cheers

I had only noticed one or two with rapid gill movement, the rest seemed to be normal (based on my limited experience). I salted when I first added them and again when the losses started accelerating so think it's around 3-5ppt.

I have trouble embedding pictures properly but hopefully these links work. They show this afternoon's casualties.

https://www.dropbox.com/s/y838rtm5gqjzt ... 7.jpg?dl=0

https://www.dropbox.com/s/extidfeh75s7g ... 7.jpg?dl=0

They look alright (for a dead fish)
How is it going at the moment? Any left?

5 left and they have been behaving 'normally' for a few days. Seems I may have avoided a complete massacre!