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Author Topic: Canít get below 1.5 mg/l ammonia!  (Read 1816 times)
New Member

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« on: May 22, 2018, 09:21:13 AM »

I have an established 46 gal bow front tank that has 11 small Glo Fish, 4 neon tetras, and 1 BN Pleco about 2Ē long in it. The tank is filtered with a marine land 220 canister filter that has a course, med, and fine sponge filter on bottom then water rises through 3 levels of bio-home ultimate media. I also have a Fluval HOB 70 aquaclear that has sponges and media also. I only clean 1 filter at a time about 1x mth and just rinse out pads in water from my 50% weekly change outs. Nitrite is 0 and nitrate is usually around .5 mg/l when I check it. I run a wastewater Treatment facility and all my numbers are run by my chemist on an $80,000 instrument! She is as familier  with the whole nitrate cycle as anyone in the country! She doesn't understand the ammonia either, but attributes the low nitrate to de-nitrification in the canister filter. This tank has been online for 8 mths. All fish seem healthy and I've had no fish kills or signs or distress. But every few weeks when we run an ammonia it's always around 1 to 1.5 mg/l. She runs QA/QC daily so I know her numbers are spot on. I just don't understand why I can't get rid of that ammonia. My tap water has <.5 mg/l ammonia in it but you would think that would convert in the filters. As mentioned I change out about 50% of my tank water every 7-10 days and always add a conditioner/ chlorine remover with the new water. Appearance of tank water is crystal clear. Fish are not overfeed and I vacuum out the substrate at every change out of water.I hope this gives enough info as I would really like to figure this out!
Whoa. Where did I put all my stuff?
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I know where rasaqua's stuff is.....

« Reply #1 on: May 22, 2018, 07:41:59 PM »

Interesting indeed. Chances are there is very very very little de-nitrification going on inside your canister filter. The media available is not standard for your canister filter and it would take a bit more monitoring to control. Not something you would want to leave unattended while on an extended road trip. Back to the ammonia issue...My first observation is that the lab-grade testing equipment would be  producing correct results compared to the standard and even higher grade standard over-the-counter store testing kits that employs in-the-ballpark results. My second thought would be to consider pH and temperature, but as you mentioned, your current filter media to bio load should be handling that ammonia. This leads me to start thinking of a greater than normal  mineralization process, but your bio load still doesn't seem to support that to the extent of the ammonia you described. Ok, the only thing I can think of at the moment is that the lab test kit is measuring total ammonia. this may seem like a crazy idea, but can the test equipment be adjusted to measure just free ammonia?

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"For every difficult question, there is an answer that is clear and simple and wrong."
(George Bernard Shaw)
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« Reply #2 on: May 22, 2018, 08:04:28 PM »

Thank you so much for taking the time to look into this! My chemist and I do have a lot of experience in de-nitrification and the control/ optimization of it. However, maybe your hitting on something with a possible mineralization issue? As I had mentioned in my first post, this tank has been online for at least 8 months now and I have never recorded a nitrate level greater then 2.0 mg/l in the last 5 mths. You would think with my fish load (not thatís itís heavy for the size of my tank) that I would have seen at least a 10 or 15 mg/l nitrate at some point. I have even tried and let my water change go 2 weeks with no increase in nitrate! We are completely baffled by this! I will ask her tomorrow if she has a way to run just a free ammonia on one of my samples(not sure if she has the correct reagents). My water temp is 76 degres. I will have to check ph as Iíve never once measured it!
I really appreciate you taking a little time to think about this because we just canít seem to understand why there is always 1 to 1.5 mg/l of ammonia present even with the advanced filtration this tank has. And, secondly, why we never see any appreciable nitrate in my water samples.
If anyone can figure this out itís someone on this forum! Thanks again!
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« Reply #3 on: May 22, 2018, 10:51:47 PM »

It's great information for those who are looking for these things.
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