False ammonia readings caused by something leaching from my sand substrate.

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Zaphod414

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Aug 2, 2020
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The long and skinny of my issue is that I have something leaching from the sand I use as my substrate that is causing an alarmingly high false reading using a salicylate based ammonia test kit (API specifically, but any test using this chemistry will most likely provide the same results). I need help identifying what this mystery substance could be.

Some more background and details are defnitely in order. I just wanted to get the main question out there on top for those that are just skimming things. I have about 25 years of increasingly knowledgeable fishkeeping experience under my belt, and have been running a 25 gal continuously without any major issues for the past 20 years. I also have a newer 55 gal running now that is established and has been in operation for about 8 months now. The 25 gal is currently a welcome tank for new arrivals to spend their first few months in and is bare bottom. No issues in there. The 55 gal, though, has a sand bottom that has been causing me some grief. It is a pure silica pool filter sand I get from a local sand and gravel operation called Shaw Resources (Nova Scotia, Canada). It's really an excellent sand that both the fish and I just love. I researched the sand before I started using it and inquired about any additives they might use that might pose a problem. It's just pure silica sand. It leaches a little bit of silicates into the water that makes the tank more hospitable to brown algae, but I easily keep that in control with a little Phosbond in the filter. The big problem is that it seems to be leaching something into the tank that is giving me a false positive reading on my ammonia test kit.

When I first established the tank, for several months all was good. Then I decided to replace my test kit reagents as the ones I were using were getting quite old. I nearly had a heart attack when I did my first ammonia test with the new kit and it basically turned black on me. Well, dark green to be exact, but the darkest reading the test can give. So I immediately repeated the test several times assuming I had messed the first one up royally, but kept getting the same result. So I tested a bunch of other water sources - taps, buckets, my 25 gal - thinking I just had a faulty kit, but got the expected 0 ppm result each time. I even tried a fresh test with the old kit and it was reading just a slight hint of ammonia itself. So I had missed the slowly accumulating problem because I was using a test kit not sensitive enough any more to detect it and jumped right into the middle of the problem with both feet. The health and behaviour of the fish has never been affected, so the through that I actually had 8+ ppm of ammonia in my tank never really held any validity to me. Everything in the tank would be long dead at those levels. I have had no deaths and the fish all appear to be healthy and normal.

Fast forward through 3 days of research and testing and I have definitively proven that the source of the high ammonia reading is the sand, and it is almost certainly not actually ammonia. I soaked some of the sand in some pure water for a while and was able to get a positive test result for ammonia from the water. The sand used in the test was from the same bag as what's in the tank but had never been used in the tank. There is some substance leaching from this sand that is causing the API salicylate based ammonia test kit to detect ammonia, but whatever it is is having no appreciable impact on the fish. Now that I am aware of it I am keeping the levels low through increased frequency and quantity of water changes, but this is not a great long term solution. I would much rather figure out what's going into the water and how to get it out. What could it be that is causing the ammonia test to react? Copper was my first suspect, but on testing the water is reading 0 ppm of copper. If the culprit is a metal, perhaps Cuprisorb would still help to remove it? Cuprisorb adsorbs a lot of different dissolved metals besides just copper. It might be worth a shot, but the stuff is pretty pricey so I'd really like some input before trying that route.

So, any theories on what my mystery substance might be? Anybody have any similar experiences with false positive results on these test kits that didn't end up coming back to copper or Prime? All input is welcomed and any insights are greatly appreciated. I will keep the thread up to date with any new developments.
 

Zaphod414

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I just wanted to add that all my test kit results have been confirmed by the LFS up the road. They get all the same results I do at home. So it is not just human error or faulty test kits, unfortunately.
 
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If you can, test for iron. That is known to interfere with ammonia tests. I cannot imagine why there would n iron in the sand. But. in an open style gravel yard it is very easy for airborne contaminants to get into the products. Other things that interfere but I would not expect are silver, lead and tin. All of these can be in ion form in water.

Can you get a recent report from your water supplier? You may even be able to find this online.
 

Zaphod414

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Acutally, iron is a pretty common element in the earth here. We even have a few stretches of road with a reddish tinge to the asphalt due to the high iron oxide content of the locally sourced aggregate used. So iron in the sand is actually a reasonable possibility. The good news there is that Cuprisorb will remove iron, so if that's what it is I have an easy way to get rid of it. Your input allowed me to find a great document from Hatch listing a whole bunch of stuff that can skew a salicylate based test. Iron is definitely the primary suspect right now. I will see if I can quantify my iron levels and will update the thread with my results. Thanks for the clue!
 

Zaphod414

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If you can, test for iron. That is known to interfere with ammonia tests. I cannot imagine why there would n iron in the sand. But. in an open style gravel yard it is
Oops, I posted my response as a general post not a direct reply as I intended. Iron is a definite possibility, as is Magnesium according to the list I was able to find thanks to your tip. Both are quite high in the area where the sand was produced. I can remove iron easily enough with Cuprisorb, but not sure about the magnesium. I will see about what I can do to quantify my iron levels and will keep the thread updated.
 

FreshyFresh

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Sorry if I missed it in here and you may know this given your 25yrs of experience, but does your water supply use chlorine or chloramine as a disinfectant? Chloramine will convert to ammonia once you treat it with your dechlorinator. If you have adequate nitrifying bacteria in your tank, this ammonia should be quickly converted to nitrates.
 

Zaphod414

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Sorry if I missed it in here and you may know this given your 25yrs of experience, but does your water supply use chlorine or chloramine as a disinfectant? Chloramine will convert to ammonia once you treat it with your dechlorinator. If you have adequate nitrifying bacteria in your tank, this ammonia should be quickly converted to nitrates.
Chlorine yes, chloramine no. I have been using Aqua Plus for years as my water conditioner but switched to Prime when this mess began. I thought I was saving money all these years, but as it turns out not only is Prime better but because it's so much more potent per ml than the Aqua Plus that it actually works out to be cheaper as well. Considerably.

My biological filter appears to be running fine by all measurable metrics besides the oddball high ammonia reading. I see the nitrates slowly rise as they should, and nitrite remains zero. The overall health and behaviour of the fish is great. So I'm not particularly worried that I'm having any problems with my nitrifying bacteria, but will continue to keep my eyes open for any signs of trouble there.
 

FreshyFresh

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You may be aware, but there's also been a phenomena reported where prime (or the granular form safe) being used in conjunction with the API master test kit can give false ammonia readings. I don't think they're drastic readings though.
 

FJB

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If the sand is indeed "pure silica sand" (as stated), and it is clean, there is absolutely no way the sand is leaching anything. Silica is SiO4. It is chemically inert, and even if it could react, there is not ammonia in it to leach. Silica is as inert as the glass in the aquarium, which is made (mostly) of silica.

If the ammonia readings are real (see good advice above for other possibilities), it is coming from somewhere else.
 
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Zaphod414

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Aug 2, 2020
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You may be aware, but there's also been a phenomena reported where prime (or the granular form safe) being used in conjunction with the API master test kit can give false ammonia readings. I don't think they're drastic readings though.
I am aware of the Prime phenomenon. It can temporarily ionize free ammonia (NH3) into ammonium (NH4+) making it less toxic to the fish while giving the biological filter some time to consume it. This does not actually cause an increase in ammonia reading on a salicylate based test because it measures both forms of ammonia. What happens is people are expecting their ammonia to drop to zero after adding Prime, but it doesn't work like that. The ammonia reading stays right where it is, only its toxicity characteristics have changes. This is a moot point in my case, though, as I had never used Prime prior to this issue showing up. I only switched to Prime AFTER all this started. I had been using Aqua Plus for years leading up to this.
 
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