Backyard Aquaponics
A place to discuss aquaponics

Hi All,

I have an aquaponics set up with a 6 ft x 3 ft x 2 ft fish tank with almost 400 litres of water. Water depth is 1.2 feet in the tank right now so it's not completely filled to its full capacity which is approx 800 litres. Tank is open from Top only a net is covering it. I have 2 Air pumps with air stones in the tank working 24x7 and i have a large power filter which cleans water and agitate water at the same time. And i have one more power filter which not just cleans water but also move water from fish tank to my NFT pipes.

The water goes from NFt pipes to my DWC growbed with 3 large tomato plants fruiting currently. i have one more air pump with air stone in my DWC grow bed too. And from my growbed water moves back to fish tank. The exit pipe is at a certain height so that water falls in my tank from approx 1 ft. So I guess that too aerate water.

Water temperature stays at 27 C at night and in the morning and goes to 29 - 32 C in the afternoon as we have summers here right now.

Ammonia, Nitrite reading is 0 at all times. Nitrates are 40 PPM. I have 1 PPT salt in my system.

My koi fish have started showing signs of dullness and less appetite from last one month and they are dying one by one. Some fish are acting okay while others one by one seem to be dull and dying. Yesterday I lost 2 small Kois and today one large koi which was acting dull for past few weeks was found dead.

One more large koi was too showing dull behavior but I shifted her to my home aquarium for 2 weeks and applied general purpose medicine. That I guess saved my Koi. She is back to normal life now as I can see her swimming really really fast when i give them food. She is eating well and behaving normal. I have again shifted her to my aquaponics tank.

None of my home aquarium fish ever die. My home aquarium koi are all looking happy and healthy. I guess water temperature does not rise over 27 C in my home aquarium at any time as it's in the room.

So what's really happening here? Why are my fish dying one by one? I am trying my best for oxygenating water with 2 pumps and water fall.

Are they dying due to high temperature? Or do you guys predict some disease? Or due to low quality food? i give them pellets only and sometimes some red worms.

Please help everyone.

90F which is around 32C is at the top of what Koi can handle. This temperature is very difficult to make sure there is enough oxygen in the water to keep the fish alive. In addition, if you are feeding during that time, it can also cause oxygen shortages due to the bacteria feeding on the waste produced by the Koi. How much air does your air pumps/stones put out? I would make sure not to feed the fish until the temp has gone down considerably (27C) and reduce their feeding. It sounds like the fish are stressed and if they get stressed they can have all sorts of health issues.

Thnxx for replying.

may be it's oxygen issue as I don't see any white spot on any of my fish and none of my koi are flashing or trying to jump out of tank. So I guess their immune system is weaken due to low oxygen. Is there a way to check oxygen levels in water?

Yes, use a dissolved oxygen test to measure the current levels. I would test in the fish tank since that's where the issue is showing up.

Hi
I am no Koi expert but I do think Carp, have the ability to gulp air at the surface. However a constant need to do this may stress them.
Reducing your PH slowly should help. Also reducing the height of water in the FT should allow a greater fall from the return thus increasing oxygenation.
The NFT tubes are heat exchangers. Can you run them from an independent water source during the heat of the day? Reconnect at night to FT
DO meters are great but expensive

How many fish do you have in the 400 liters(100 gal)? And sizes/weights? Titus brings up a good point... what is your pH level?

I had 9 fish. 4 of them died. So now have only 5 Koi. The biggest koi is 4 inch long.

pH is 7.4

I am increasing water now to make it 600 litres. may be more water will have more oxygen.

One more tiny fish died today. not sure what's happening. Is it due to lack of oxygen or temperature swings. I had almost 400 litres of water in the tank, does that cause temperature swings?

Generally the more water you have the less violent the temperature swings are.

today one more milky koi not eating. I shifted her to my home aquarium as I don't want to wait and let her die in my pond.

What the hell is happening? I added 2 PPT rock salt a month ago in my pond as I saw my koi flashing and after i added salt all of them stopped flashing. Is 2 PPT salt killing them slowly?

Shall I change 50% water of my pond which will be almost 250 litres.

Are there bacteria in my pond which are slowly killing my fish?

How will I know what is causing slow death of my koi one by one.

Here is a pattern.

1. First one of my Koi reduce eating and become lethargic.
2. then after a few weeks they stop eating if I don't shift them to my home aquarium at this time for 1 week then I loose them.
3. If i leave the fish in the pond then they slowly starts bottom sitting and eventually die in a week or so.

Any help is appreciated.

PS. If I shift my fish to my home aquarium then in a week they magically become healthy and hearty automatically. My home aquarium is just 120 litres however my pond is 600 litres large surface area with aquaponic setup to clean water. i change water in my home aquarium not in my pond. Pond only gets water when water evaporates.

Sounds like definitely water quality issues. I would check pH, temp, ammonia, nitrites at multiple times in the day. Something is not right and causing the fish stress. Look for temperature swings and pH swings as causes. Where are you getting your top up water for the pond?

My bet would be on the temperature swinging too much putting stress on the fish. Do you have a picture of your setup? With a pic we might be able to see something that we are missing with just words. What is shaded and what isn't, that type of stuff. Unlike your inside tank that has it's temp regulated by the house. your outside one is in direct sunlight. MB's make really good heat sinks. Allowing your water to either gain or loose temperature rapidly.

I just noticed this in your post. Please tell me this is a mistype. You are only supposed to salt to 2 PPM. 2 PPT would be WAY too much. To give you a reference, the salinity in the ocean is approximately 32 to 35 ppt.

Someone suggested 2 PPT salt to stop flashing (1 PPT is 1 kg salt in 1000 litres of water).

I also added 200 ml liquid seaweed extract in it to aid micronutrients in water for plants. I have been added sea weed for quiet a long time and never had an issue.

Is 2 PPT salt too much?

Also I checked pH today morning and it was 7.6, i will check it again in afternoon and at night to see if it fluctuates too much.

Temp today morning was 29 C and in afternoon it was 31 C. I will check temperature in evening and night too and will update on my next reply. Also I will add pics of my setup in my next reply.

Too much salt can become an issue, 2ppt is fine, and won't cause an issue. But the seaweed extract is high in salt, and if you've been adding it continually, it might be bring it up too high. Depends on how much you've added though.

Can you test the salt in the water?

But I'd imagine the plants would die off before the fish.

And is the seaweed extract you're using pure, and organic, or mixed with fertilizers?