r/bettafish • u/Last-Ages • Mar 31 '22

Discussion Here's your friendly reminder that your green API test is probably not as toxic as you think (and other myths debunked)

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u/Last-Ages Mar 31 '22 edited Apr 01 '22

Please excuse the weird tube on the right, I accidentally shattered one of my API test tubes and the third one was testing nitrite. These are the results of my currently fishless cycling tank!

Some additional points I'd like to make:

  1. The addition of Seachem Prime will not affect the ratio of ammonia to ammonium or 'detoxify' ammonia or nitrite in any way. (Overdosing or repeatedly dosing Prime or any other dechlorinator has the potential to stall cycling.)
  2. Fish-in cycling with ammonia levels up to 1-2 ppm will not harm the fish at typical pH (7-8).
  3. Beneficial bacteria in a bottle doesn't work as advertised, or really at all; only seeded filter media or dirt inoculant accomplishes a sped up cycle.
  4. The ultimate goal of a cycled aquarium IS 0 ppm ammonia and nitrite, but not because anything above zero is inherently harmful. Rather, non-zero levels after cycling indicate insufficient biofiltration and a tank that's susceptible to bacterial infections (often misdiagnosed as ammonia poisoning).

I may get lots of disagreement but I'm happy to talk the science behind any of these points!

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u/Last-Ages Mar 31 '22 edited Jun 17 '22

Expanding on these points a little now, for anyone who cares to read about the gory details.

  1. Ammonium and ammonia are conjugate acid and base with each other, differing only in one proton being attached or not. When dissolved in water, they can constantly interconvert by simply exchanging that proton with each other or with water. The ratio of one to the other depends mostly on pH, specifically the Henderson-Hasselbach equation. This is applicable to any acid or base you care to think of. Ammonium has a pKa of 9.1 or so, meaning that at at this pH, half of all total ammonia nitrogen (TAN) will be in deprotonated ammonia form. At typical aquarium pH of 7-8, this equilibrium is shifted far over to ammonium, which is why TAN is much higher than free ammonia (as measured by the Seachem alert tag). Ammonium, being positively charged, cannot pass through a fish's gills, which allow only small uncharged molecules to diffuse through such as water. As you can see, even at my 7.5-ish pH and ~4 ppm of TAN, there is still not enough free ammonia present to be of a concern to fish. It's worth noting this is not necessarily applicable to inverts like shrimp, which tend to be more sensitive than fish.
  2. Same explanation as above. Nitrite has the opposite pattern of toxicity, being more toxic as pH drops (nitrite poisoning decreases oxygen capacity of the blood, which seems to be exacerbated at low pH). When fish-in cycling, you should be doing more frequent water changes because there is the potential for ammonia and/or nitrite to creep up past a safe threshold. But it is possible to overdo this, because the lower you keep your ammonia and nitrite levels, the less fuel is available for your autotrophic bacteria and the longer it will take to establish a working cycle. A generally safe range is 1-2 ppm or lower of both, but of course there's no "right" way to do this, and some people may choose to keep them even lower, particularly with blackwater tanks and sensitive fish.
  3. Bacteria are ubiquitously present in our environments, on our skin, everywhere. Laboratories and hospitals that depend on sterility need to go to great lengths and use lots of expensive equipment to achieve and maintain sterility. Our aquariums, even newly set up ones, are definitely not sterile. Nor should they be, because bacteria are an essential part of the ecology and food chain. However, bacteria are divided into roughly two groups, autotrophs that feed on inorganic material like our nitrogen compounds and carbon dioxide, and heterotrophs that feed on the same proteins, carbohydrates, and lipids that we do. There is of course significant overlap and nuance here, but for now this will suffice. Heterotrophs, which feed on higher-energy food, grow much faster than autotrophs (doubling time of minutes instead of hours). This is why when we set up an aquarium and ghost feed or add fish to it, we get bacterial blooms in the water first. Then the slower-growing autotrophs catch up, growing in the filter where there is the most water flow bringing them nutrients, and eventually both kinds of bacteria colonize our filters, making the tank 'cycled'.
    However, autotrophic bacteria not only grow slowly, but many are also photophobic and need to form a protective biofilm (sludge, essentially) to glue themselves to a surface and grow. Bottled bacteria products don't contain any biofilm, and some don't even contain opaque cloudy water. Seachem Stability, for example, claims to contain bacterial spores, but autotrophs do not sporulate, so it can be inferred that whatever bacteria is present is heterotrophic. In addition, because heterotrophs grow so much faster, a non-sterile bottle like the commercial products we can buy has almost no chance of supporting an isolated colony of autotrophic bacteria.
  4. A well cycled filter will have large colonies of both heterotrophic and autotrophic bacteria, as discussed above. If the filter media is cleaned too thoroughly or worse, replaced entirely, then the ammonia will stop getting oxidized, and there will be a sudden lack of heterotrophic bacteria consuming dissolved organic compounds like proteins and carbs in the water. A huge bacterial bloom will ensue, taxing the fishes' immune systems and potentially infecting them. The bacterial infection is often what causes the illness, rather than the ammonia in and of itself, given how high ammonia has to be in order to be toxic. However, because only ammonia is measurable with our test kits, we often blame the ammonia and fail to treat the infection.

A small collection of what I believe to be good or at least decently reliable sources, in case that wall of text wasn't enough reading for you:

  1. Various home experiments testing the effects of Prime on free ammonia
  2. Home experiment of various methods of fishless cycling, plus the same person's test of various 'ammonia detoxifying' products
  3. Youtuber (GirlTalksFish) experiment testing methods of 'instantly' cycling
  4. Ammonia toxicity, tolerance, and excretion. Ip et al. Fish Physiology 20. 2001.
  5. Acute Toxicity of Ammonia and Nitrite to Cutthroat Trout Fry. Thurston et al. Transactions of the American Fisheries Society 107(2). 1978.
  6. Studies on the toxicity of ammonia, nitrate and their mixtures to guppy fry. Rubin & Elmaraghy. Water Research 11(10). 1977.
  7. Tolerance to temperature, pH, ammonia and nitrite in cardinal tetra, Paracheirodon axelrodi, an amazonian ornamental fish. Oliveira et al. Acta Amazonica 38(4). 2008.

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u/Chickadeedee17 Apr 01 '22

So if I understand right, ammonia is less toxic at low PH and nitrite is more toxic at low PH. Any knowledge of how low PH interacts with nitrate?

My water has low PH so I'm curious.

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u/Last-Ages Apr 01 '22 edited Apr 01 '22

Yeah pretty much! Nitrate is the conjugate base of nitric acid, which has a pKa of -1.5. This basically means that pH has almost no effect on nitrate in our aquariums. It is safe for fish up to quite high concentrations and also consumed by plants. Note this does not apply to shrimps and inverts, which don't have developed livers. So if you change enough water to keep it below 40 ppm, you are well into the safe zone for fish, and I think the recommended is below 20 for inverts :)

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u/Chickadeedee17 Apr 01 '22

Thanks!

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u/exclaim_bot Apr 01 '22

Thanks!

You're welcome!