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Hello all,

I am having a hard time understanding why the ammonia levels in my system wont come down.  I built the system based on a basic IBC design.  I put a 1-ton fish tank underneath a ~1/2 ton growbed of equal diameter, slightly offset.  I put a bell siphon in the grow bed and a pump in the fish tank and filled it with tap water.  Since it's outside in direct sunlight, I figured the chlorine/chloramine was gone within a day or so.  

Then I plumbed in PVC piping around the ring of the growbed to distribute water evenly to 6 fabric bags which I filled with hydroton.  I figured it was a good enough way to start the biofilter until I was able to get enough hydroton to fill the whole growbed.  So for a while, the growbed was about 1/2 media in fabric bags, and 1/2 just space for water to fill up.  This system for the growbed lasted for a while.

Then, somewhat fortuitously, I got 12-15 young tilapia for the tank.  Since I hadnt had a chance to dose the system with ammonia to build the biofilter, I figured this first cohort would be my ammonia source.  They were very small for a relatively large volume of water, so I was hopeful they would survive the inevitable ammonia buildup while the biofilter got going.  ... and most of them did survive.  I got a very conventional ammonia --> nitrite --> nitrate curve, and all was good for a while, as ammonia and nitrite both eventually came down to near zero.

As the fish grew up, one became a bully and killed all his neighbors.  I got a new cohort that were larger than the bully.  Again, all was good for a while.

Then I decided to 'fix' the growbed by getting enough hydrocorn (slightly different than hydroton apparently) to fill the entire growbed.  I obviously had to rinse the stuff first, and I tried to let it dry before putting it into the growbed, but I also added a radial flow filter and an external sump, so I had to add some water straight from the tap to keep the pumps from running dry.

That was a rough day, so I basically assumed that I had sterilized the growbed with all the chlorine/chloramine from the rinse and top-off.  And I figured I'd just start the system over again... right?

... wrong.

That was about 6 weeks ago.  Ammonia went up and stayed there.  I use the dropper and eyeball it against a yellow/green scale, so I dont have specific numbers of exactly how high... but it's been at least 4 ever since.

Nitrite also spiked shortly after the upgrade, but it has since come back down.  And nitrate has always hovered around 5-10.  

For the past week or two I have been cleaning everything super-diligently.  I siphon the fish tank and the radial flow filter at least once a day.  I also back-wash the connection between the fish tank and the radial flow filter, which I did for the first time 3 days ago, and did get some sludge come out.  I backwashed that connection again today and it was squeaky clean.

I also systematically started doing minor water exchanges.  I fill a 55-gallon barrel with tap water every morning and let it sit with vigorous aeration until the following day.  Then I siphon about half of that barrel into the system to offset the amount of siphoning and backwashing I am doing.

Yet ammonia is STILL super high.  

So, please help.  Ideas...? Suggestions...? Questions...?

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Pics of the whole setup.  I did a few more upgrades that I forgot to mention in the narrative above.

I forgot to mention the pH has been steadily rising since the new growbed went in.  It used to steadily fall, requiring pH Up to keep it high enough.  It's currently hovering around 7.1, so I have not done anything to manipulate pH in a long time.

I was thinking about slowly bringing the pH up, as I read that nitrosomonas prefer 7.8 - 8.  At least for a little while to kick start the nitrification.  Thoughts?

Randall Wimbish said:

Test your incoming tap water with the API ammonia test kit. Chloramine will test positive. I am thinking your water changes are your ammonia.

Interesting thought.  I will try that tomorrow morning.  Thanks!

Randall Wimbish said:

Test your incoming tap water with the API ammonia test kit. Chloramine will test positive. I am thinking your water changes are your ammonia.

This morning I took a sample of water from my degassing barrel and ran it through the ammonia test.  It came back positive.  Small result, but a result nonetheless.  

So it does seem that I've been dosine with chloramine every day.  Whooops.  I guess that means chloramine takes more than 24 hours of bubbling in Florida-sun-exposed barrel to eliminate.

To deal with this, I stopped the siphon/top-off system entirely.  Also, I took the sunshades off all the ancillary barrels (sump and radial flow filter) to get maximum sun exposure on the water in the system.  

I also have access to ClorAm-X.  I added roughly 1/3 of what the box says to add based on my water volume.  I want to avoid an ammonia spike while the ClorAm-X breaks down the Chloramine.  I figure better to add this stuff slowly and see how the fish deal with it.  I will keep a close eye on the little goldfish in the radial flow filter (which I put in as a remedy for mosquito larvae - works great, by the way), as I suspect they will succumb to an ammonia spike before the adult tilapia in the culture tank.

Update: Ammonia and Nitrite have bottomed out.  It took about a week after adding the new systems (fluidized sand bed and two towers) to see any impact, and then levels dropped rapidly.

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