Fish of the Month!
- Jul 2, 2020
- Reaction score
Very interesting info I keep soft water fish because as tap water goes mine is soft maybe middling maybe more suited to Central American’s rather than south but still fit the Gh of 7dgh and always research the fish I buy to check but normally go on the rule of if they are South American it’s cool , never thought a Gh of zero could be inhabited for more than a few days , do plants still grow without the nutrients in the water ?This needs explaining to avoid misinformation. And I am only responding with respect to your freshwater fish tanks questions, not marine.
Each species of freshwater fish has evolved to function in very specific water parameters; there are some species that have a wider tolerance than others, but for the sake of this discussion let's take the majority. Many, in fact just about all species that live in very soft water such as the Amazon basin, do not need any mineral in the water; they don't have it in nature, they don't need it in the aquarium. Ian Fuller [an authority on Corydoras species] keeps his wild caught Corydoras in pure RO. My tanks are all zero GH/KH because (luckily for me, as I like the soft water fish) that is what comes out of my tap--our water here is zero GH/KH. These fish thrive in this, because they are designed to by nature.
Other species that live in water that has calcium and magnesium (the basic GH minerals) need those, and if the tap water source is not sufficient, they must be added. Livebearers for example would die in my water without mineralization to increase the GH (and pH, this tends to follow when we are dealing with RO). There are other fish in between, needing some re--mineralization. But it all depends upon the fish species' natural requirements, and our being able to provide them. Not all fish can live well in the same water parameters.
The pH of pure RO water would be 7, neutral--neither acidic nor basic. Such water does not exist in the habitats of fish because water is a powerful solvent, and readily assimilates substances it comes into contact with, such as minerals dissolved from rock or organics causing acidic water. Rain begins as pure condensed water but as it falls it usually assimilates CO2 making it acidic; depending where it lands, it may assimilate other substances, changing its composition respecting GH, KH and pH.