Backyard Aquaponics
A place to discuss aquaponics

Hi All
I have 2 IBC fish tanks each running to its own growbed and then running back to a combined sump. The sump pumps back to each fish tank and to 2 float tanks. This is the thrird system I have setup, the largest by a long way but also the only time I have ever lost a fish - and they are all deas.
This sytem is fairly new and I had cycled it with some seasol. All way going well with some healthy plants- strawberries, lettuce, silverbeet and chillies.
I have been tracking the water chemistry as I do when first establishing a system and it has been ok
Ammonia 2.5 mg/l Nitrites 0.5 Nitrates 20 pH 6.7, Temp 25-27, dissolved oxygen 98 sat

Put 50 silver and 50 jades into each tank 2 weeks ago and all way great. they were going nuts at feeding (which was cool to watch). I has 1 dead the day after adding the fish then no others until 2 days ago when there wer just 2 more then dozens the next day and pretty much the rest are now gone. I have retested the water and nothing has changed.
The fish (although dead) look ok but may have a small very fine coating on then - could be from the growbeds although the rocks were well washed and I have a decent filyer system on my pump.

Ideas anyone? Given the water chem looks ok I don't think there is a need for draining the system. Could It be overfeeding? I have been careful with this but also have not had so many fish in a tank before.

Hi RayM....

So 100 fish in each tank? That's a lot of fish, I'm assuming that you have just the one growbed off each fish tank by the sounds of it? How big are the beds?

The ammonia sounds a bit high there, not great for the fish, was that after they died or before?

Hi
Sorry, its only 50 fish per tank (100 in total) and the 0,25 is for total ammonia. The NH3 is therefore essentially zero at this temp and pH. It is the current and past value and when doing the initial cycling I spike with real ammonia (since I have access to it) and wait for it to calm down and be cyclable via nitrate formation before I ever add fish. This value has been consistent since before adding the fish and has been fine in other systems I have established in the past.

I have never had fish die like this before and am thinking it may be a pipe a had to join with the plumbers blue glue but I have never had a problem using it in the past. It did happen after a day or rain so maybe something leached from the new shadecloth into the system??? That would be real annoying given I built the shade structure purposely for the system.

I use that glue all the time so it should be ok.... Perhaps some contamination?

I remember a long time ago I lost 5 or so trout after a rain, never worked out what had happened or if it was even related to the rain.

Were the SP and JP from a shared water system or even the same place before you put them in your tanks?
Might be some sort of cross contamination..

Thats really nasty when fish die for no apparent reason. Had trout do that last year and never figured out why and two batchs of them. The system they died in is now running jade perch that are booming along and before the trout had jade perch that got to small plate size. Still dont know what happened
Sorry, no help but just needed to talk

I picked up the fish 2 weeks ago from SEQfish. They were very helpful and as I understand it they are from seperate ponds. My water is all connected so a cross contanination could do it but the fish themselves were kept seperate so they did not eat each other (as the jades grow so much faster). The Jades had already doubled in size.

I am trying to work out what to do next. Should I dump some water (my system holds around 3000-3500 litres in total or just chuck in some more fish or go back and add some more ammonia and make real sure it is cycling. I set it up at the very beginning of december and cycled it until the 11th of january so I am pretty sure its cycled. The plants are doing well.

I have evn used seasol before so dont think that could be it unless it gave a short sharp nh3 spike that I had not seen in my testing. So hard to know.

Its just frustrating not having a reason.

your pretty safe with the seasol, I spilled a heap in mine once....no effect on fish.

How do you cycle with seasol?

How do you support 100 fish with what I assume would be cut ibc growbeds of ~600 litres?

Did you get the usual Ammonia spike, Nitrite spike and then have both Ammonia and Nitrite go to 0 in 24 hours?

If your dissolved oxygen is 98 sat, does that mean you have 2 litres of water per 100 litre of room?

I suspect your fish died of water quality issues relating to not cycling your system properly.

Thats a good point, you cant cycle with seasol as it doesnt contain any ammonia. Charlie Carp you can cycle with. And with that many fish you are going to get problems in those sized tanks. How much growbed volume do you have ?

Hi All
Sorry but it seems you have misread my comment. It was cycled (with seasol in it - not with seasol. It was cycled with lab grade ammonia as I indicated later as I have access to it.

I now have a fairly positve explanation for the deaths - killed with kindness, let me explain.
For those who don't quite understand dissolved oxygen and sat levels, it is the amount of oxygen dissolved in the water in mg/L divided by the 100 percent value for the temp of the water. As most will know the hotter the water the less oxygen will dissolve. After discussing my siutation with several biologists I know it appears that when the rain came the temp dropped and my dissolved oxygen level became oversatuated ie over 100% sat. This is very bad for fish even for a short time and will cause a range of issues such as small gas bubbled blocking hearts etc. Can be much worse for small fish and fingerlings then for larger fish though it can still kill them.
In my prevuious systems I never had air stones and never had so many piped draining across rocks or splashing back into the sump or back into the fish tanks. These along with the air stone in each tank was just too much kindness and when the temp dropped even a little when rain was around the oxygen spiked and caused a silent killer. I did not measure the oxygen levels when it was raining so don't have a value to offer and the fish did seem a little bloated when dead and it also explains why ALL the of chem tests were satisfactory.

Given I have some 5 m square of growbeds (with space for 2 more, and 2 float tanks and splashing back into a sump and this splashing back into the fish tanks it is getting more then enough oxygen without me using bubblers as well.

This may laso explain some of the unexplained deaths others mentioned especially after rain. Hope it helps shed on light on things.
I feel more confortable now going and getting more fish knowing what may have been my previous issue.

I doubt over saturation of oxygen was the cause, although possible it usually would be caused by a rapid addition of cold water to a system, where the higher level of DO in the colder water is released as it mixes with the warmer water. Although the rain water was probably colder than the system water, I don't think it would go in quick enough to cause this to happen.

If you don't quarantine your fish before introducing them to your system, then you are taking a risk of introducing parasites or diseases. The fish you buy usually come from a large mass of water compared to fish mass, so when introduced in to your system this is reversed and any parasites that the fish may carry can quickly multiply and find a host easier.

Actually I think the deaths were from cross contamination..

2 different fish species from 2 different ponds and 2 different forms of bug's..

Poor QT procedures..

Better to go slow and safe..

Juergen