1.1.4. Water Parameters

The water fish swim in is very important. But it is not nearly as important as people give it credit for. The chemistry of the water, the pH, the hardness, and the salts contained in the water, are just not very important to the well-being of the freshwater tropical fish.

If you can drink the water, fish can thrive in it      

So do not buy a test kit with your new aquarium. Just add a de-chlorinator if one is on a municipal water system and GO. Add fish when you are ready. And simply do not worry about the water. The “water parameters” are just not that important.

Tanichthys albonubes White Cloud Mountain Minnow
Tanichthys albonubes White Cloud Mountain Minnow

Water Parameters in More Depth

Note EVERY time I say that water parameters are unimportant on social media the number of fish police who come out of the woodwork to say “That’s not true, you idiot” are amazing. But it is simply true! Add conditioner if the water had chlorine in it and you’re good to go. The following points are pertinent:

  • The water in the aquarium needs to be as bacteria-free as possible. This requirement is important but rarely even mentioned or discussed. The bacterial count correlates with the water clarity. “Crystal clear” water is very low in bacteria while “dull” water is very high in bacteria.
  • Close control and stability of temperature in NOT important. Temperature for almost ALL tropical fish can range from 70 to 90 degrees F. (21 to 32.3 degrees Celsius), with the occasional excursion to 65 degrees F (18.3 C.) to 95 F (35 C.). And fish are not “shocked” by rapid changes in temperature.
  • The pH of the water is not very important. Most tap water between a pH of 6.5 and 8.5 is fine for all fish. Some fish require water like their native waters for breeding. Beneficial bacteria need a pH higher than 6,5 to process ammonia.
  • Hardness (both GH and KH) is of little consequence except in that some KH hardness stops a “crash” or “old tank syndrome” from occurring. “Old tank syndrome” can’t occur if one does 50% water changes every one to four months (depends on stocking levels).
  • Salts are not important so long as most fish have a little. If one has RO water they take on more significance. The only time fish can get in trouble is if a fish is put in very salt-free (total dissolved solids or TDS less than 60) water. If one only has a meter which measures microseimens, multiply microseimens (EC (μS/cm)) by 0.55 to get an approximate ppm TDS (sodium chloride) equivalent.
  • The idea that water has “heavy metals” or “toxins” in it is a huge myth, propagated by those who sell products “designed to remove the heavy metals and toxins”. Isn’t the profit motive great?
Glowlight Tetra
Glowlight Tetra

Water Changes

There is a myth that one must change the water in an aquarium at least once a week. This idea is patently false. We recommend a 50% every two months to four months, depending on stocking. These “water changes” ONLY take out nitrate from the aquarium. Water changes do NOTHING else in the aquarium.

Note many very experienced hobbyists do no water changes and do just fine. There is a whole fish store in San Francisco that hasn’t done a single water change in ten years with what are probably fifty or sixty aquariums.

The only reason to do water changes is to keep the nitrates low. And nitrates are just not very toxic. If one does water changes according to nitrate level I recommend water changes only if the nitrate goes above 80 ppm. Note nitrates are ONLY reduced by water changes or plants. Here is an article on it:

5.4. Safe Nitrate Levels

Xiphophorus maculatus Pineapple Candy Platy
Xiphophorus maculatus Pineapple Candy Platy

Myths About Water

There are many myths about the water in which aquarium fish live. Some of these myths are:

  • It is essential one has a water test kit and that one tests the water frequently
  • At least 50% water changes should be done once a week.
  • It’s dangerous to the fish to “chase” pH with chemicals.
  • High pH (>7.5 pH) is dropped by using organic materials such as almond leaves, beech leaves, oak leaves, peat, and/or driftwood.
  • The “water parameters” shown by water test kits are important when diagnosing fish diseases.
  • Fish will have their lives shortened if put in a pH different than their native waters.
  • Fish from the Blackwater Amazon will suffer in water with a high pH.
  • The hardness (GH and KH) of the water is very important to the fish.
  • Fish will have their lives shortened if put in a water hardness different than their native waters.
Corydoras rabauti
Corydoras rabauti
  • Rapid changes (in seconds) in water parameters (pH, hardness, and/or temperature) can damage or kill freshwater fish.
  • Temperatures need to be closely held for healthy fish and heaters are an absolute necessity in most homes.
  • Stability in aquarium parameters (temperature, pH, hardness) over hours or days is important.
  • Nitrates going above 10, 20, 40 or even 80 ppm will shorten the life of an adult fish.
  • Ammonia levels at some level below 5 ppm or nitrite levels below 1 ppm are detrimental in any way to fish at a pH of 7.
  • Ammonia levels at 5 to 10 ppm or nitrite levels from 1 pm to 5 pm are very toxic to fish at a pH of 7.
  • When shipped fish are un-bagged, they should be gradually acclimated to their new water chemistry.
Gymnocorymbus ternetzi Veiltail Black PhantomTetra
Gymnocorymbus ternetzi Veiltail Black PhantomTetra
  • Water that has been run through a water softener is bad for fish.
  • Water changes remove built-up toxins and fish hormones in the water.
  • Water changes are bad because they cause variation in the water parameters.
  • Primetm and Safetm are superior water conditioners that also “neutralize” ammonia, nitrite, nitrate, and heavy metals.
  • There are products that “neutralize” ammonia and nitrite (Tetra AquaSafe Plus, Kordon AmQuel, ClorAm-X, Hikari Aquarium Solutions Ultimate, SeaChem AmGuard, API Ammo-Lock, API Stress Coat).
  • It is beneficial to add “bacteria in a bottle” such as Stability for every water change.

All these myths are simply false

Golden White Cloud Minnow
Golden White Cloud Minnow

To go into the subject of Water Parameters in more depth click on the following link:

4. Water Parameters


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Translated in dutch by : Joost Abrahams
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