Backyard Aquaponics
A place to discuss aquaponics

Hi All,

I am new to AP and this forum and chasing a little advise.

I have an old spa I have converted as a tank just shy of 3000 Litres and 4 grow beds made from two IBC's cut in half. I had 13 Koi and 6 freshwater catfish for 3 months and then added 120 Silver Perch.
The system has been operating well until my pump packed in - I replaced it the same day but then started losing fish. Not sure if this was coincidental or not. I went away for 4 days (a friend looked after the place) upon my return I had lost all my Koi but 1 (the biggest one) and all my catfish.
My PH level is currently 7.6 and I added 3 kg's of salt to combat the loss of fish.

Today I lost 6 of my Silver Perch and others are at hanging around just below the surface, lying on their side or swimming very lethargic.

I have attached some photo's of my system and of one of the dead fish.


I would be very appreciative of advice of how to save my fish.

Thanks

The other tests that you could try would be ammonia and nitrite and water temperature.
Can you scoop the bottom of the spa to see if there is any uneaten food or dead fish contributing to poor water quality?
Umm friends feeding fish - a story that worries me, as I hear it often. Did you restrict the feed so that they weren't fed too much? Floating or sinking pellets?
Sorry that I am asking more questions than giving answers.
Fish are not like cats or dorgs and will go days and weeks without being fed, though the silver perch would nibble at the duckweed and biofilm if they are hungry. Leaving them for 4 days would not have been a problem.
It looks to me like you have around 8oo litres - but no more than 1000 litres of filtration. We recommend no more than 50 fish at the maximum and feeding needs to be increased slowly as adding 120 will require the bacteria to catch up and be able to convert the ammonia.
Keep us posted Homemade! The photos are a great help to understand a system, thanks for that.

Thanks for the quick response.

I scooped up the dead fish - some of which were stuck to the pump. I should have been more specific on the feed (sinking pellets) as there was a bit on the bottom.

I will carry out the tests for ammonia and nitrate and let you know how I go.

Thanks

Hi Homemade, one of the reasons that we use floating pellets it that you can see if the fish are eating the food or not. If the feed is till floating in half an hour scoop it off. Often if it settles it fouls the water, contributes to poor water quality, breaking down consuming oxygen at the expense of the fish. I think that is what happened plus the fish deaths causing ammonia and a domino effect. Withold food for now, clear your water a little perhaps by pumping full time, adding salt was good.

Thanks for that it helps a lot.

As above...

Thanks RupertofOZ.

Would there be any benefit in transferring fish to another tank?
Dump the water in spa and start afresh?

Everytime you interfere with the fish you cause them stress - scoop the tank, catch them, move them etc, etc etc. Take a back step, do the water tests and leave things alone.
Too many people do too much - less is more. And one step at a time.

Your problem is related to the number of fish you have... and oxygenation...and if you can find a way to oxygenate more... then that would be beneficial...

Spreading the load across tanks would help in that regard... but ultimately... you're still way overstocked for the amount of filtration you have....

But if you have another tank... then you could... and the fish are "small"... and you have some time available... to get at least twice as many grow beds online....

Otherwise... splitting them... and getting an air pump would posiibly help... although a number of the fish might be permanently damaged from oxygen depravation already...

Faye makes a valid point... that your fish are already stressed severally... and moving them now would only stress them more....

You water return to the tank seems minimal.... are you running a timed flood & drain??

If you are... switch the timer to "always on"... and run the system constant flood until you get more beds...

Your priority is to try and get some more oxygenation happening...

I have the system on constant flood and drain now.

Okay thanks I do have another IBC so I will set that up as soon as I can.

As the others have said, Homemade, highly overstocked beyond the capacity of your system.

Chalk it up as a learning experience. And don't don't worry, you're certainly not the first or the last.

Thanks chillidude.

Faye, RupertofOZ and chillidude really appreciate your time and for sharing your knowledge.