Backyard Aquaponics
A place to discuss aquaponics

Hi guys asking everyone that I can, currently have big problems with my fish.

We are losing fish every day and I have no idea why. We have always lost a few fish every time it rains a lot over a few days and we have always put it down to the rain water dropping the PH level.

At the moment we are losing up to three fish a night and it is the bigger ones. Started with all the ones that were ready to eat. The ones left all look healthy and moving away fast, in the afternoon, and you can not predict the ones that will be in trouble the next day. As they die they firstly slow down and then begin to float upside down and then die.

We have completely stripped the pump and tank to ensure nothing dead anywhere and we have a bit of stringy algae on the edges of the tank but nothing huge. We have even changed the bellows in the compressor to ensure adequate air output.

The current levels are

PH - 6.0
Ammonia - 0.25 ppm
Nitrite - 0 ppm
Nitrate - 10 ppm

The garden beds are half full of veges and they seem to be growing well.

If anyone has any ideas we are open to any ideas.

Many thanks

Hi Peter,

What are you testing your pH with?

What sort of fish?

Just adding to the above with a little more info that was missed.

Firstly I am dealing with Silver Perch and the other thing is that the last storms actually doubled the amount of water in the tank.

Been doing a lot of reading in the last few hours and everything seems to be leading to damage caused by rapid PH change but of course I am still guessing and open to any advice.

My other question is that my PH is always low around the low 6's What is the best way to keep the PH a little higher and possible stop the massive drops when it rains...

Also is it worth covering the tank when large amount of rain is expected.

Thanks for any help supplied.

re-posted here as I am still new to site... sorry for duplication if I have.

I have silver perch and they vary in size from 15 to 30cm in length.
I am using a API Freshwater Master test Kit

If you're using the API test kit and your pH is reading 6.0 then your pH could actually be much lower without your knowing it - 6.0 is the lowest the test can read. It's possible that you need to adjust the pH up although this may not be the cause of the fish problems it could be a contributing factor.

If you have quite a bit of algae growing in the tank it can cause the pH to fluctuate and can use up the oxygen at night.

Your statement about the rain dropping the pH makes me wonder what the pH of the rainwater is, especially since the tank water pH seems like it could be low. It also makes me wonder if something toxic is being carried into the tank water. Where does the rainfall runoff and does any of it go into the system. Are there any metals, pesticide or treated wood sources that the water might drip off of?

Sometimes after an ammonia or nitrite spike you will lose fish gradually like this because of damage that occurred so there may not be much of anything you can do about it if this is the case.

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Things you can do to help the fish for now.
1. Increase the oxygen levels
2. Salt the water to 1 part per thousand with sodium chloride (potassium chloride will also work). This will help with nitrite poisoning and also help the fish with stress and building a slime coat.

Pictures of your system might give us some other ideas

P.S. - I already took care of the duplicate post

Many thanks.. When I mentioned rain water I was referring to what fell from sky into tank and beds nothing has been added from tanks...

Any suggestions on what to use for PH reading and how to increase PH.. I have always had a problem with low PH..

I did salt after the first few deaths.. Any time I add water to tank I fill a 400Lt tank with tape water and let it sit for 3 days before adding to tank

Going to work... will post some pics when I get to work

To test below pH below 6.0, you can use a low range pH test kit, or even a better, a digital pH meter. They are much more accurate, plus very fast and convenient.

To raise and buffer (make it stable for longer) your pH, you want something with a carbonate in it, such as Potassium bicarbonate.

Using just Potassium bicarb on it's own will harden up your water solve your pH issue, but you need to be aware that there is a 3-way relationship between Potassium, Magnesium and Calcium, in that if you add too much of one, you reduce the ability of the plants to absorb the other two, leading to deficiencies.

I use and recommend a combination of products, which are allowing me to keep my pH in check, but also giving good plant health. I'm currently using Calcium carbonate (crushed limestone, sold as garden lime), Calcium Magnesium carbonate (Dolomite lime), Calcium hydroxide (brickies lime), and Potassium bicarbonate... in a 6:2:2:1 ratio.

I add the Calcium carbonate, Calcium Magnesium carbonate, and the Potassium bicarbonate directly into the FT first, wait for about half an hour, then add the Calcium hydroxide (made into a runny paste) directly into the GB at the water inlet, when the GB has just finished a drain cycle.

The Calcium hydroxide will do most of the pH raising, this is why I add it to the GB at the end of a drain cycle, so it has time to mix with a decent volume of water before it's dumped into the FT.

Mine is a single IBC system with a 500L FT volume, the pH can get down to around 5.8-6.0, then using proper measuring spoons I add:

1x tbsp (15ml) of Calcium carbonate
1x tsp (5ml) of Calcium Magnesium carbonate
1x 1/2tsp of Potassium carbonate

Then half an hour later:

1tsp of Calcium hydroxide.

This combo usually brings my pH up to around 6.4, but it will vary for every system, depending on water hardness.

I'm currently doing this twice weekly because my system is overstocked to buggery, so there is a lot of nitrification taking place. I've got about 9-10kg of Silvers in a system that should have a max of 7kg... I will get around to eating a couple more soon.

P.S. I clean the floor of my FT every Sat' arvo. I use a siphon vac to remove any visible fish waste solids. While I'm doing this I also siphon out the sand left over from the Calcium carbonate (crushed limestone), as it tends to collect in one corner. This way I don't get a build up of it in the FT. I use the Calcium carbonate so it gives a slower release of carbonates over a few days. It works much better than chunks of limestone, gave up on that.

Many thanks for all of the information, I will start by getting a PH meter on Monday and will start to slowly increase and see how I go.

Just before work checked as I took the photos and found another dead. Was able to check gills and they were nice and pink.

Have tried to attach pics hope they come through

I have been doing aquaponics for almost 4 years now and I had the same problem for over 2 years. Many people had good ideas that work for them, but as for me my fish kept on dying. Although the water levels were within the reasonableness I couldn’t figure it out
I salted the fish, I drained the water, I lowered the Ph, etc. I lost all my catfish twice, then all my goldfish twice and then my perch started to die as well. I tried different fish to see if the problem was the breed of fish I was raising.
My water is rain water and it is goes through double filtration, with an acid ph, which I balanced by adding lime stone to my water reservoir.
Anyway, It wasn’t until I started to do a research on aquaculture that I came to the realization that the water was the problem, I read that if you can not drink the water were your fish live, then your fish will suffer. If one fish gets ill, all the fish will get sick as well. I solved the problem by adding a UV filter before the water goes back to the fish tank. I haven’t have any dead fish ever since.( about a year) My system is 250 square feet of media and a water draft of another 150 squared feet. Now I can say, that I learned one lesson, maybe there is more to it, but for me it was a great relief.
I hope that this helps.

Clay balls and rain water will maintain low ph. Excessive rain water can mess up the chemical balance supporting your aquatic environment, covering (GB's & FT) and capturing rain water is a better idea. Adding chemicals to adjust the ph can have you chasing your tail.
Creating another inline bio-filter or GB with washed scoria will lift the ph.

It sounds like some disease of sorts possibly brought in from your fish supplier? Sometimes it can take a while for the bad bacteria to build in the system. Are you running constant flood? Did you salt bath quarantine your fish before adding to your system?
If it is a bacterial disease then what Susan says makes sense with the uv filter.