Backyard Aquaponics
A place to discuss aquaponics

Hi, I have just lost all my trout over the last week. The issue now is I had all my levels sorted as follows mid week when the deaths slowed down.

Wednesday they were
PH 7.6
Ammonia 0
Nitrite 0
Nitrate 40

The last 10 died this morning, I have not feed them this week and have salted twice.
the levels today are
PH 8.4
Ammonia 1
Nitrite 0
Nitrate 10

Any ideas on what going on with the levels and how to I get the PH back down?

G'day Mate

may not be able to help but a little more info on your system and i think you might get some more answers

properly need size, stocking levels, how long have you had the system running, the more info the better, even if it's for barra in summer.Sorry to hear about the fish Hang in there.

Those levels are all over the place. Something must have happened for the ph to change that much, but I reckon it was just a dodgey ph reading. Make sure you rinse the testing tubes real good before testing.
The ammonia is probably because of dead fish
More info needed. Tank volume, growbed volume, how much aeration and what system of growbed draining, ie, flood and drain with constant pumping and autosyphons, or with timed pumping?????
With dead trout (manto furiously knocks on nearest wood), lack of aeration is the first place to look, from my reading of these forums.

Hang in there dude

And maybe another question might be media....what sort is it ?

At this point all fish have died and as the levels continued to change. PH up to 9 and ammonia and others down to 0. I have pumped all water out to containers. I had a look at the pond bottom' Mostly just a bit of sand on the bottom. The water is very brown. There was no smell until I got down to the last 200m of water in the tank that smelled like all kinds of hell. I cleaned it out let the other water stand for a while and pumped back about 750lts of the original 1000ltrs. I am going to add some limestone rocks to try and get the PH under control. Hopefully once all is sorted I can add some barrumundi. At the moment I have a 1000ltr tanks and 1 x 500ltr grow bed. The fish almost certainly died from over population and not enough aeration. I have added a massive aerator with 6 ports for future use and I am hoping to add another grow bed soon. I am using large pea gravel for the media and the plants have been going nuts. I will post some pics after I get the water levels today. Thanks to all for your help.

HI RK
My only comment would be to add more GB's, at least another 500lts

No, no, no ... limestone will not move your pH in the opposite direction from where you are now... it will merely keep the pH where it is... or worse...

Might have missed it but what was the temp of the water.

rkdraft, yes agree with Rupe. Limestone is used to buffer/increase pH not lower pH.

Firstly, are you using bore water to top up your tank?? If so, what is the pH of the bore water??

You said your tank water is brown in colour... Is it brown like this?? Don't look at the airstone but the water behind...


If so, it was the same colour I had when half of my first batch of trouts died. Did not read your posts but did you have green or greenish water before the trouts starting dying??

If so, you could be the algae present in your water that is swinging the pH... How you can confirm that is to take a pH test this thing in the morning and last thing in the evening... If the pH of the water without any rain/top-up swings, then you have algae in the water... pH swings themselves are usually stressful to fishes...

And the algae also creates another problem... they compete for oxygen with the fishes during the night... (if I get my basic science correct)...

Getting down to the last 200mm of water and it smells really bad, could this be a solids buildup on the bottom of the tank ??? Sure smells of it

My pond colour is about the same colour of brown. How do you get rid of the algae without killing the plants?

thanks for the heads up on the limestone.

I use tap water which is normally around PH of 7.2.

been raining today so will try some more test tomorrow.

The best way to get rid of algae is to deprive the tank water of any sunlight. So cover the whole tank with a thick tarp.

Also I would add that I believe the BYAP Golden Rules leaflet did mention that you should not feed the fishes when your tank is having a pea soup stage (ie. algae bloom). After my last bad experience, I only feed the fishes in the day when I can see them feeding and when the water is relatively clear such that you can see the bottom of the tank (although this could be a bit hard to get used to initially when the bioslime builds up.

Algae would explain the PH swings. I had the same problem. Covered the ponds for 2 weeks with black and white poly plastic. Algae died and the ammonia spiked up to 2.0. After that I uncovered it and the algae disappeared. From what I was told the dying algae actually inhibits more algae growth, so it might be good not to change the water next time it happens.

I have finally found what is causing the brown water and High PH. It appears that after about 6 weeks or so the bulk of the clay sediment on the pea gravel has loosened and resulted in the color change and as clay has a high PH has increased my level in the water around about 8.4 and up. Only remedy is to flush the grow bed and change out the water.

Looks like a great weekend for beer and swearing.

Ah yea, reasons to wash gravel.