Why is my ammonia high in a larger tank?

Brooke DeVol
last month

In the spring my husband built me an outdoor fish pond/table for our patio. This was just as COVID Hit. I found myself struggling with mild depression during quarantine and sitting watching the fish listening to the fountain made me feel much better. I found myself sitting by the fish table daily.

The tank was only 60 gallons. I started Out with 3 Shubunkins. Wanting a few slightly larger fish I added 2 comment goldfish. Being food hogs they quickly grew from 2-3 inches Up to 4.

Here is where the problem really started. My husband mentioned how much he liked a blue koi we saw at a koi farm. Thinking this would be a good gift I brought home 2 small koi.

Everything was fine and the fish healthy and growing. I had a 200 gph pump/filter later adding another pump rated at 300 gph and even with the tank overstocked at this point the water never tested above .25 ppm for ammonia and zero Nitrates or nitrites. If the tank was over 0ppm I would do a partial water change until we were back to zero.

I am embarrassed to say by the end of summer I had four Shubunkins and 6 koi. Two koi had grown from 2 inches to around 4 inches. The others were still very small.

I started reading multiple articles for n both Shubunkins and koi care and including a plethora of forums. I made just about every mistake a new fish owner could make. I didn’t have a pond as an option at this point.

Even with my extremely overstocked patio pond I never tested above .25 ppm for ammonia and zero Nitrates or nitrites. ph was stable at 7.5. If the tank was over 0ppm I would do a partial water change until we were back to zero. I used Prime as my water conditioner.

I knew I needed a temporary solution to get the stocking levels down and a much larger tank. I purchased 3 180 gallon stock tanks for the fish and am housing them in my green house.

I have a major ammonia problem now. I’m confused that with so much more space why I am having significantly more problems. One tank will be zero for a few days, the other is constantly hitting .25 daily, and today one tank skyrocketed to 2ppm. Normally it would be .25 never this high. The pumps I had weren’t cutting it and extremely hard to clean and keep clean. I was rinsing the foam daily. So I have three new pump filter combos rated at 660 each. I changed the media out to Seachem Matrix. Soaking all of the new filter pads and media in the old tank water and water from the old filters for three days.the daily water changes are unsustainable and it it seems significantly more stressful for the fish.

I also keep trying to balance the size and type of fish per tank to evenly spread out the bioload. I now have 7 Shubunkins. Two comets, and 10 juvenile koi. The only thing I can think of is adding another stock tank. I’m running out of room and could swing a 75 and if pushing it maybe 110. Although not the best option two 40 gallon stock tanks are the best option space wise.

I know I made major mistakes along the way and I am doing the best I can until the pond is completed. I need advice on how to get the ammonia levels to a consistent 0ppm and away from constant water changes.
What are my options?
Thanks you for your patience with my long post. Yes, I know I made irresponsible choices. Please do not berate me. I feel bad already. I just really want to keep my fish Healthy and happy until I can give them an appropriate home. Thank you.


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