Backyard Aquaponics
A place to discuss aquaponics

We have a fairly new system (about 4 months old). We have alot of plants growing that are doing very well.

We cycled the system for 6 weeks before adding the fish (rainbow trout) that we purchased from a local farm. For our system we can have up to 20 trout but we decided to start off with 10 just incase we got anything wrong.

When the fish arrived, we actually had 9 as the farmer miscounted. We lost one on the first night as the silly thing jumped out of the tank (after that we made sure the tank was closed with netting.

After a few days, we started to loose fish. They were floating/swimming either sideways or upside down - poss swim bladder desease? Now we only have 2 left. one of the fish arrived with a scar on its head - we thought poss been fighting, though I just read about a parasitic infection that can cause scars on the head?

All of our readings are good - PH, amonia, Nitrates, Nitrites etc. Water temp is high though for trout - sometimes getting to 26c. So we want to get perch instead as we think could be better for our temps.

The question is, when can we swap to perch? would they be ok with the other 2 trout that are left? Should we do a water change first incase of desease?

any help and advice welcome!

Welcome to the forum Fermedulynx .

Sorry to hear about the fish deaths. Without knowing for certain what killed the fish it's pretty much impossible to tell you whether it's OK to add the perch but I can tell you that the trout will probably eat the perch if they are big enough and are given the chance. If the size difference isn't that big you might be able to get away with it.

I doubt it was a disease that killed the trout but it is possible. It sounds like the water temps may have been marginal and maybe the oxygen levels dipped or stress got them. If you haven't hit your summer high temps the trout probably aren't going to make it without some additional help.

Yes we are at a bit of a conundrum really We dont want to sacrifice the 2 fish that are left, but at the same time, the hard work of cycling the system and getting the levels right for all the plants we now have. i am now concerned that 2 fish are not going to be giving enough to all the plants and also that the bacteria might die off if not enough waste is there to 'sort out'....

Release the 2 trout into the river as they would have been if still at the local farm and start again with perch or wade it out?

Bonjour fermdulynx,
Salt your tank.1-2ppt.
It sounds like they are dying from the move, may be pH change, temp, nitrite poisoning or o2 issues.
Best not releasing to a river.
The bacteria will not die off, it takes years to fully build a healthy bacteria colony.
What size are they?
Rainbows are a bit of a tricky first fish however once you get a bit more experience they'll be fine.

26C is too hot for Rainbow Trout, even if adding plenty of aeration. I lost a few due to heat at around 25C last summer.

skeggley -the 2 that are left are about 25cm long (well one of them is, the other seems alot bigger but its tricky to find him as he hides alot.)

They both eat very well. I feed them in the morning before the sun gets too high and watch them to make sure.

When you say salt the tank - what kind of salt is best to use?

For oxygen, we have an air pump in the tank, as well as lots of return pipes flowing back in from a height. PH has been steady at 6.8 and we always top up from rain water. (our tap water is source too so there is no cholrine or floride in it).

we suspect the temp is the problem and poss the stress of moving from the farm. We are building a new tank in the ground outside for them.

One thing that has occoured to us; our tank has a simple overflow that feeds into our sump (where the pump is) The oferflow is taking water from the fish tak at the top of the water level. Would it be better to devise somthing to "up-take" water from the base of the fish tank? We seem to have a build up of sludge.

Ok what Gordon says is true, 26°c is too warm, didn't see that, likely the cause of fish death. 250mm is a large size to transport in numbers and 20 would contaminate the transport water pretty quick if < 40 litres....
Here we run trout wintertime as temps aren't suitable summertime. I reckon you'd be in the same situation.
As for what salt, pool salt is the best, cheap and is generally free from additives.
Plenty of air will help however it's generally more trouble than it's worth in my opinion.
Having said that, if you can keep them until spring/winter you will have 1kg+ fish next summer.
In the higher temps feed minimally if at all.
Supplement your plants with seasol or the like meantime if you choose to try to carry the fish through summer.
Hope this helps.

Ok thanks. We will get the new tank outside built ASAP and hope that these guys last in the meantime. Atfer they have been moved will top up with more trout outside and get perch for the inner IBC.

Both fish seemed happy today and water temp was alot lower (22c) but as July approches that will get worse.

On the plus side, our plants are doing really well and i think we will be eating salad all summer from the garden