Backyard Aquaponics
A place to discuss aquaponics

After playing around with general concepts with a couple of buckets, I have finally got my income chop and flip system cycling,
600l fish tank
300l grow bed,
But only put in three goldfish (because I didn’t want them to die during cycling like they did in my mini system.)
Now I’m Thinking that’s way too small an amount of fish, and that maybe I should add more? Like 9 more?
Love to hear your thoughts



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I recommend fishless cycling and many weeks of time. Add one tsp per day of clear ammonia. Test ammonia daily. Adjust additions to keep the ammonia between .5 and 2 - this is not good for fish. Once you are adding a consistent amount of ammonia daily and the ammonia starts to go down, cycling has started, continue adding the ammonia daily and test for nitrite daily too. The nitrite will go up for some time (this will kill fish), but after some weeks it will start coming down. Once you are adding daily ammonia and the ammonia and nitrite are 0, your system is cycled. This typically takes about 8 weeks depending on temp and pH (which should be ~6.5 if I recall).

Now you can add fish. If you are going to stock heavily, expect an ammonia and nitrite spike, which can kill your fish. Only feed the fish if the ammonia and nitrite are under control. Remember the cycling just gets the bacteria colonies started, they need time to mature and become robust.

Three goldfish is probably a good number for cycling a system of that size with fish. They will provide the Ammonia required to get the bacteria colony established without much prospect off a dangerous level of Ammonia building up before the system is cycled, especially considering you are in NZ and heading into winter, with cold water temps it would take a considerable amount of Ammonia for it to be toxic to your fish.

I would run the three goldies for at least a month, then gradually introduce more in small numbers, ie: 2 or 3 at a time a couple of weeks apart, until you get up to your desired level, testing Ammonia, Nitrite and Nitrate regularly in between additions to keep an eye on how cycling is progressing. In your winter it could take 6 or 8 weeks to cycle. In a single IBC system like that you could safely run 20 goldies, or more, once fully cycled. If you can get them up to that number by spring you could then starting planting out more heavily.

Thanks for input guys.

Have kept the three for now, but have yet to read any ammonia levels at all. Planning to start adding feed every day to try and get sone kind of Ammonia level reading at least.

In other news, my smaller test system seems to have had this nitrite eating bacteria moved in, and is fully cycled.
Time to start feeding them more or adding new more fish!




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It has been a week, and still no signs of ammonia in the tests, thinking we need more fish.
Doubling to 6?
Is this a bad idea?


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Hi mate, I wouldn’t have thought 6 goldies in that volume would be overloaded but I’m no pro and it is a new system.
Fish feed will also contribute to the ammonia values and specific goldfish food is usually designed for minimum impact.
That’s not to say your system isn’t converting the ammonia already, I never saw ammonia in mine after the first few weeks.
All the goldfish I’ve tried to grow in my system finished up out of the system in the worm farm... I have seen AP systems run on goldies successfully though.

Yep, more fish... Of course there's goldfish and then there's goldfish, how big are they? Personally if they are 2-4 inches I'd stick 6-8 in now. Just watch your feeding rates, remembering that feed is the major input into the system rather than just having the fish in there..

I would say they would be between 1.5 - 2 inches long. Just younguns.


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Any advice on a good feed for goldfish available in nz?
They don't seem to excited about what I'm throwing in there, and I'm purposefully over feeding, but still ammonia hardly registering, tho I do think I detected the tinyest of movement yesterday after adding three more fisgfor a total of 6


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So my large system looks to be cycled?
Started reading ammonia straight after adding the extra three fish, and stopped feeding when nitrites started to spike, however have resumed feeding and still reading trace for ammonia and nitrite.

This seems incredibly fast tho considering the temperature and predictions of taking 2 months.

The tank is positioned pretty near a compost pile though, could that have helped to kick start the cycling process?


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