Backyard Aquaponics
A place to discuss aquaponics

Hi All,

We started out aquaponics system about 2 months ago. It is a 60 gallon tank, swirl filter, with about 40 plants in PVC pipe. We started with 3 feeder goldish to cycle the tank and then added 20 tilapia fingerlings. After a few weeks the tilapia started to die off. They would lay on the bottom and open and close their mouth. They were dyeing at a rate of about 2-3 fish per day. After a few days we decided to put the fish in a salt bath (separate tank) and to add a small amount of salt into the main tank and all of the tilapia died within the next 2 days. We then decided to stick with goldfish. We had the 3 original goldfish and 15 more small comit feeders. The feeders started to die off in the main tank and now have all died. At this point all of the water chemistry levels are where they should be, and we have been aerating our water for several days in order to remove chlorine. We believe that we have bacteria or parasites in our tank and we need some advice. We are considering another salt treatment or using MinnFinn. Has anyone ever used MinnFinn and is it safe for our plants/our health? (we wont be eating the fish, only the plants) Also, at what level does the salt kill our plants?

Moving forward we plan to quarantine fish for 2 weeks before adding them into the tank. Is there any treatment that you would recommend? We are planning on upgrading to a 120 gallon tank and expanding the system but would like to figure our what is killing our fish first. Any feedback is much appreciated. We have learned a lot from the forum already, thanks for that.

Sounds like stress die off. What was your water quality and how did you aclimate them?

Also I would fishless cycle next time. That cause a lot of health issues in fish and severely shortens their life. If you nuked the system do a fish less cycle before adding new fish

Use the drip method to acclimate new fish. Takes a while to do but i havent lost fish since I started using that method. It takes about 2 to 4 hours. But once you get it going you can walk away.

-Put your new fish and store water in a container.
-adds an airstone for gentle airstion. Of you don't have a valve then tie a granny knot in the airline.
-take a section of air tubing long enough to go from your tank to the container of new fish. Start a siphon and tie a granny knot. Tighten the knot until it drips a couple drops a second. Now let it drip into you container of new fish.
-once the water level doubles in the container dump it and let it double again. Then you just gently transfer them from the container and add to your tank. Dump that water.
-top up tank with new water.



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Stress on them starts the moment they are caught, bagged, stored, transported, then dumped into a new inviroment. Often times the acclimation to the new inviroment is is the straw the breaks the camel's back and they can't cope and drop like flys.

There is always pathogens in the water. If they are over stressed they are easily susceptible.

For over stressed fish and poorly acclimated I always see two die offs at rate of 1 to 3 a day in newly added fish. The first week are the ones that were just too tramatized. Second week are the ones that had a weekend immune system and basically get a fishy cold or what ever pathogens naturally in the water.

I addmit to being a fish serial killer until learned about stress, fishless cycling and drip acclimation.

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Sorry to hear about the fish.

I would hold off on using the MinnFinn, I don't think your system has parasite problems.

A lot of times with parasites the fish will flash. This is where they are trying to remove the parasite by flipping on their side to scrape against the bottom. If they aren't doing this but are just laying on their side gasping at the bottom then I think something else is going on.

The stress suggestion is a good one and may be right although I think this is a filtration issue because the system you described basically has no biofiltration. You need surface area for the bacteria that process the ammonia excreted by the fish. Plants only process nitrates, bacteria do the Ammonia to nitrite and nitrite to nitrate conversion. Do you have some media anywhere in the system or a biofilter? I caught that your tests aren't showing any ammonia... but the test kits are occasionally faulty and even though things may be working and the parameters look great now, it's also possible that the fish suffered gill damage from an earlier nitrite spike which was missed. This is pretty common in new systems because the biofiltration may not be ready to handle the load and often isn't as stable as what an older system would have.

For now I would -

1. Make sure you have adequate biofiltration (something like a growbed with media or a moving bed biofilter for example). If you don't have filtration or the filtration isn't adequate, stop or reduce feeding. Fish can go for days or weeks without feeding - small fish are a bit less durable this way but still are pretty tough.

2. See if your test kit is faulty by taking a water sample to a pet store (most here in the states will check it for you). Might not need to do this if you're pretty sure it's working but at least check your procedure on how you're running the tests.

3. Aerate the water as much as possible.

4. If the water in the tank doesn't have salt at this point, then I would salt the water with 1 part per thousand of NaCl (table salt/pool salt, use the kind that isn't iodized and doesn't contain anti-caking agents). This helps the fish build a slime coat and helps prevent nitrite poisoning.


There are a couple of things that you should look at doing for the next time you get fish, if you didn't do them this time.

1. Fishless cycle using something like seasol powerfeed or ammonia without other additives. This lets you beef up the filtration a bit to handle larger loads before the fish go in. Don't overdo it on the ammonia, too much is not a good thing.

2. Make sure the water is salted as mentioned earlier. Strawberry plants don't like the extra salt so skip this if you're planning to grow strawberries.

3. Do the best transfer you can to prevent shocking the fish. It's best if the pH and temp are close between the two waters (if they are way off sometimes the fish will act stunned or lay on their sides near the bottom - I did this once so that's how I know) but keeping them in a transport container for too long is not good either as the water quality will get worse.

4. Once they are in your system start them with really light feeding and check on the water parameters as you increase the feed over a few days - to be sure the filtration is working.


I tried to cover everything but I'm sure I missed something. Do the best you can and don't hesitate to ask questions. It's pretty common for people to lose fish when they are getting started, most of us have been through this.

For a biofilter I have filter bags filled half way with clay pebbles
When I first started ammonia and nitrite spiked but all numbers are 0 now ph is 6.6-6.8
I put my first 3 goldfish in different tank because they were just sitting on bottom after about 5 days they looked better swimming around eating
I put them back into Aquaponics tank 1 each day and they were fine for 3-4 days now they are sitting on bottom swimming occasionally
I have been aerating water before adding to Aquaponics tank
I used top fin water conditioner in quarantine tank
Yesterday added some vitamin C to tank to see if it was a Chloramines issue
Not sure what else to try
I’m using nfs system with sewer grade pvc
Plants are doing ok
Thanks for any tips

If you had Chlorine or Chlormine in the water you would have an ammonia spike and dead fish with chemical burned gills.

Though I have read you can add untreated tap water up 10%. I don't trust it that though.

What is your water temperature? If it's under 65*F fish start slowing down, eating less and hanging at the bottom. Also Tilapia need to be kept above 65 or 70*F. They start kicking the bucket under that.

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Water is 66

Post up some pics of your system, might give us some other ideas. Sometimes certain metals or some other item that is toxic to fish can cause something like this.

Did the water from the the tank you transferred the fish into come from the same source as your system water, where they are having problems?

Water in quarantine tank is city water treated with top fin water conditioner
I started system with half city water and half rain water collected of top of pool that was half frozen at the time and I heated it by my wood stove
Just been using aerated city water for water changes since
No heater on system just room temperature that goes from 65-80