Toxic Water Chemicals

[10 Tanks]

Hello TFF. What are all the chemicals in a fish tank that need to be rendered non toxic or removed from the tank water to keep the fish healthy. I can list the following: Chlorine, chloramines, heavy metals, ammonia, nitrite and nitrate. Have I missed any?

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[Essjay]

You have listed all the things we routinely worry about.

Chlorine needs to be removed, usually by converting it to chloride. This is done by using a dechlorinator found in almost all water conditioners.
Chloramine needs to be removed. Water conditioners split chloramine into chlorine and ammonia, and remove the chlorine usually by turning it into chloride. But the chemical that splits chloramine and removes the chlorine part leaves ammonia in the water.

Ammonia in tank water can come from splitting chloramine and from fish waste. When it comes from fish waste, ammonia-eating bacteria and plants remove it as soon as it appears; there may be trace amounts presents at all time but in such small amounts that we cannot detect it.
Ammonia from chloramine is a different matter as that is added all at once rather than in tiny amounts 24/7. For this reason, many water conditioners contain a chemical which detoxifies ammonia for around 24 to 36 hours, and the bacteria/plants should have removed the ammonia before the detoxification wears off.

Nitrite should not be present in a cycled tank. This is only made by ammonia eating bacteria converting ammonia into nitrite; it is not added with tap water unless there is something wrong with the tap water. The only time nitrite should be in a fish tank is when the fish keeper is doing a fish-in cycle, and then the fish keeper should do water changes to remove it, or add salt to protect fish from harm until enough bacteria have grown to remove nitrite as soon as the ammonia-eating bacteria make it.
There are products which claim to detoxify nitrite, again for around 24 to 36 hours by which time the nitrite eating bacteria should have removed it. Seachem Prime and API Aqua Essential both detoxify nitrite; there may be others. These should be used in conjunction with water changes to protect the fish from the nitrite made between water changes.

Nitrate is the end product of the nitrogen cycle. In nature more bacteria convert nitrate into nitrogen gas but these don't often grow in fish tanks. Water changes are done to remove nitrate, though both Seachem Prime and API Aqua Essential temporarily detoxify it.
When a tank is heavily planted, very little nitrate is made in the tank because plants take up ammonia as fertiliser and they don't turn it into nitrite and on to nitrate.
Many places have high levels of nitrate in tap water. The US allows 45 ppm on the scale used in fish keeping, for example. The only way to keep nitrate low in such places is to remove the nitrate from tap water before it is added to the tank.

Metals are present in most tap water, some places have higher levels than others. Most water conditioners contain a chemical which binds metals, so they are no longer free in the tank water.




A number of fish keepers have tap water which they feel would be detrimental to fish. Maybe there's a lot of nitrate or metals; perhaps the water is very hard and the fish keeper wants to keep soft water fish. One solution is to use reverse osmosis water which will remove almost everything dissolved in tap water. Some use 100% RO water, others mix it with some tap water, and others add remineralisation salts to put back small amounts of minerals.

 

[10 Tanks]

Hello again. Thank you. So, what I'm understanding, is that if I continually remove these subject chemicals from my tank water, my fish should remain healthy. Is this what I'm reading? My aim in this is to use nothing but regular tap water, nothing as fancy as RO or distilled water to achieve a balanced water chemistry.

10

 

[Essjay]

You do not need to continually remove ammonia and nitrite as the bacteria and/or live plants will do this for you. I know you do a lot of large water changes, but you will also have both ammonia and nitrite eating bacteria in your tanks, and if there are any live plants in your tanks, these will also remove ammonia.


Depending on the source of your tap water, you could have chlorine or chloramine. Well water has neither but mains water usually has one or other. Chlorine can be removed simply by letting water stand in a container for a few days. Chloramine, on the other hand, does not gas out so this needs water conditioner to remove it. If you are on mains water, your water supplier should be able to tell you which they add.
Chlorine and chloramine both affect fish skin and gills which is why they need to be removed.


Metals can be quite high in some well water; mains water usually has mandatory limits on the amounts allowed - a water quality report from a water supplier will say what's in mains water. Wells are usually tested to make sure the water is safe for humans to drink; the test reports should say what's in well water. Water changes with high metal content tap water will not reduce the amount of metals in tank water.



Nitrate. This depends on two things - the level in the water you add to the tank, and whether the tank has a lot of live plants. Lots of water changes with high-nitrate tap water won't remove nitrate as it'll be added with the new water. Low nitrate tap water will remove nitrate with water changes. A water quality report/well test results should give the amount of nitrate in tap water.
Live plants will significantly reduce the amount of nitrate made in the tank from the ammonia excreted by the fish. A lot of fast growing plants may also remove nitrate from tap water if they have used up all the available ammonia.





Your water changes will remove the things excreted and secreted by fish, things that are not removed by micro-organisms in the tank. An example is the hormones secreted by growing fish fry which in some species can inhibit growth of smaller fry so fish breeders do lots of water changes to remove this hormone.

 

[gwand]

API Nitro Absorb Actually took my tap water nitrate level from 30 ppm to around 5 ppm. But the bag that the resin is contained in is not made for hang on the back filters like the kind I have. It was very bulky and slowed down the water flow through the filter. So I had to remove it.

 

[GaryE]

There are always ifs. It doesn't really matter how water you change if the fish you keep has water needs you aren't meeting. An Amazon tetra in very hard water, or a standard molly in soft water isn't going to be healthy. If you or I drop onto the summit of Mount Everest, it isn't going to matter if the air is clean. We aren't adapted to such low oxygen, or cold, and we'll die. Fish are adapted to conditions we should respect.

Tap water is a tough phrase. In my life, I have had 350ppm, pH 8 tapwater, 140ppm 7.4 water, 80 ppm pH 6.8, 50ppm pH 6.6... all of it came from different taps drawing from different aquifers, rivers or lakes. If I told someone with hard water how to keep a fish from my soft water, I might give very bad advice unless I were aware that a "tap" is device, not a type of water.

Plus, clean clean water is not going to eliminate parasites and pathogens. The right water changed massively will make fish stronger and better able to fight back, but it doesn't guarantee they'll win.

I change a lot of water as often as I can, and don't need to be convinced of the positives. But it's just part of a big picture.