Aquaponic Gardening

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Hi again.

I bought three little Tilapia from an aquarium shop to cycle the system with them but they did not survive. I suspect the problem was that the system is a bit rough for small fishes; I think they could not swim much because of the current of the inflow/outflow in the bathtub. Could it be that the fish tank doesn't get enough light? Or that the system is outdoors and during the night might be cold? The indications of PH and ammonia are not to worry about (still a bit alcalic though) and there is still a small indication of surviving nitrates. The tomatoes seem to be doing ok. Do you think I need bigger fish? Where do you buy fish from? I live in Germany.

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It's hard to respond with an answer yet. Can you give us a bit more information?

What type of tilapia did you buy and how big are they?

How long did they last?

How big is the tank?

Did your system fully cycle (reach highs in ammonia, nitrites and nitrates before settling down)?

How long has they system been running?

Do you have plenty of aeration?

How cold does it get during your nights?

What kind of system are you running?

Light can be a problem; but more for the plants than the fish. Ambient sunlight should be enough for the fish.

For my system I bought from two local growers, and now am breeding my own, which is a project in itself!

Hello Sheri, thanks for your response!

The tilapia were pretty small, I dont know the type but I can find it out if it's very important.You can see a picture.

They lasted about a week. The tank is a bathtube, about 300 lt.

No, my system was not cycled. I could not find ammonia source and decided to cycle it with 3 little fishes. I ve followed the instructions of the aquarium shop stuff and put in my medium a bacteria product that I bought from them.Two weeks later (the system had be running for 2 weeks), some nitrates appeared in the test and the aquarium shop stuff told me it's ok to put fish in.

I don't have an aeration device. I have built a flood and drain system with siphons that works very well and have put the water inlet at the fish tank a little high so that there are many air bubbles (not sure if that helps).

I dont have a water heating device either and the weather has been pretty bad lately in Berlin, it can drop to 13 degrees during the night.

As regard the light, I have covered the bathtube with a plank to protect from children and dirt. Was that really stupid?


No, Valentina, nothing is stupid if you learn from it! :) I asked about the type of tilapia because each kind has different temperature ranges. I don't think any of them can handle 13 degrees, though, so the cold temperature is likely one factor. We're growing Nile Tilapia because we live in a desert and they can handle higher temperatures. Colder regions usually raise perch or other cold water fish. 

Aeration would be another factor. The water flowing in helps, but given the size of the tank, you probably need a good bubbler as well. You can usually tell this by watching the fish. If they hang around the area where the water's flowing in and creating bubbles, they are trying to get air.

I also think the board over the tank is a problem. The fish need light, at least 12 hours/day.  It doesn't have to be direct sunlight, but it doesn't look like your tank allows much light at all. Depending on how far north you are, you may even need to add a light to the system to extend the day.

From what I can see, your fish are, perhaps, a couple inches in length? Given their size and the size of the tank, it'll take a long time for ammonia to build up and start the cycling, and then the cycling usually takes a 4-6 weeks. The bacteria product helps speed up the cycling, provided you have some media it can grow on. Your grow beds may suffice for that. Your blog pictures show that you're using Hydroton (clay balls). That's a good choice. It holds water well and has ample surface area for bacteria to grow on. Have you seen any spike in ammonia or nitrites, or only nitrates? It's a good sign, but I'd question whether the tank is fully cycled.

I would recommend you find a fish that can handle the cold temperatures better. You can try perch or catfish, or if you're not growing them for food, good old goldfish are great. I would also recommend you add a bubbler and cover the tank with a clear plastic cover. I think your fish were probably affected by all three things. Good luck, and let us know how it goes!


Hey, thanx for the tips- It's a bit more clear now...I will see what kind of local fish I can find, I was thinking to go to the river and catch some! If they survive the cold river they will survive in my system as weel. Anyway, I am looking for possibilities to move it indoors for the winter. I will also fix the light-aeration problem.

No no spike of ammonia since I haven't add ammonia at all. It is impossible to find clear ammonia, I went everywhere. I might try again thought with fishless cycling, but I ll have to use urine as source.

I saw on your blog that you were aging some urine to use. Many frown on using human urine, chicken waste and goldfish to prime the system because of the potential for introducing harmful bacteria and disease. That said, I think a calculated risk is OK as long as you take precautions and are willing to suffer consequences if it goes wrong. We used goldfish to get things started and some chicken manure to speed things up. They worked very well. We took the goldfish out a few days before introducing the tilapia to make certain there were no parasites.

A word of caution about using wild fish: they're more likely to carry parasites, bacteria and disease than purchased fish, so start them in a separate tank (a bucket with aeration usually can suffice). After you know they're healthy, you can put them into your system. If you get fish from multiple sources, introduce only one fish from one source to the fish from the other source. Watch it for about a week to make certain it stays healthy. If it does, you should be OK combining all the fish.

You have a great project going on there! It'll be fun to watch as it progresses. :)

Thanx for having a look at the blog and the possitive feedback! And for the tips!

I opened the urine that I bottled a month ago and it smells really bad and I am really hesitating to use it.The PH is about 8.5. I will try a bit harder to find clear ammonia. Somebody told me to look at a place that shell materials for photography..

I found out about a fish farm a bit out of Berlin! They have carps. I will buy there some, so no need to risk with wild fish, even though it would have been fun fishing them!

You're welcome! 

If you can get a handful of carp, you won't need the ammonia. The urine might smell bad because it's turned to ammonia, which would be a good thing. But I don't know too much about old urine, since I try to avoid having it around. Ha!

Is the 8.5 PH in the urine or the water in your tank? If it's the tank, your water is high like ours. To lower the PH, get some peat moss and fill an old nylon stocking, then float it in your tank. It will help lower the PH, which will keep your plants much happier. It will turn the water brown, but the carp won't mind.

Go ahead and fish for the wild fish...and have a good dinner! :)


"If you can get a handful of carp, you won't need the ammonia.": Do you mean to do cycling with fish?

The 8.5 is in the urine, but the water is also alcalic. Around 8. Peat moss?? I was just reading that is hard to find...In germany everything is even harder to find!I 'll have a look anyway, thanx!

One more question: do you thing it is possible to feed the carps with dead wasps and flys? There are plenty in the garden and I could catch them and freeze them or dry them. I am interested in non-processed feed..

Yes, if you can get carp, they can get the cycling going because their waste will turn to ammonia. Carp are very hardy, and can handle the spikes in ammonia and nitrites better than many other fish.

The urine is such a small amount that it won't affect the PH of your entire tank, so it shouldn't be anything to worry about. But you want to bring the PH of the tank down around 7 if you can. Ireland is loaded with peat moss-that's what makes up their Bogs. Maybe you can take a trip there. LOL!

We get peat moss at any nurseries (plant & garden store) and home improvement stores here. There are other things you can use, too. Just think about it: PH measures the acid and base balance. The higher the PH is, the more base it is. The lower the PH, the more acid. So you want to add acid to bring it down.

You don't want to use the aquarium chemicals because you'll be eating the plants. Vinegar can be used, but it's not too stable. Another option is wood. Not wood with a lot of sap, like pine, but wood with tannins, likw nut trees are good. But you want to make certain you've boiled it first to kill any bacteria, and you have to be patient. Now that I've told you all that, I'll give you the easiest way to fix the PH problem: use water that's been through a reverse osmosis filter. It usually has very low PH.

As for fish food, carp should be fine with bugs, dead or alive. That's what they eat in nature. They're scavengers, so you can also throw some meat and veggies in there. They like duckweed, if you can find some in your area. Maggots and blood worms (which are mosquito larvae) should make them very happy, too. Experiment with things to see what they like. Just keep a good balance between protein, fat and carbohydrates.


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