TDS in hard water

[aarhud]

Is TDS a useful parameter for fish that require harder water? Or is it neccesary to only rely on pH, gKH, and GH?

 

[Simon Morgan]

GH is only part of the story so it's good to know TDS if you have a meter. I honestly don't test for GH any more because using a TDS meter is quicker and cheaper. pH and KH are still important IMO for Hardwater species, and especially for keeping a healthy filtration system. IME it's easier for softwater species to tolerate hard, alkaline water than is for Hardwater fish to survive the opposite.

 

[gerald]

TDS is NOT useful for determining whether your water is suitable for hard-water fish. Hard-water fish need Calcium and Magnesium (GH) for mineral balance and growth, and they need alkalinity (carbonate and bicarbonate) to keep the pH high. Water with salt (NaCl) added will have high TDS, but it may not have any GH or KH that the fish need. TDS is really more useful for softwater-fish, where you want GH, KH, and all the other ions to be low, and for brackish water fish that need a certain range of salinity.

quote="Simon Morgan, post: 79727, member: 799"] I honestly don't test for GH any more because using a TDS meter is quicker and cheaper. pH and KH are still important IMO for Hardwater species, and especially for keeping a healthy filtration system. IME it's easier for softwater species to tolerate hard, alkaline water than is for Hardwater fish to survive the opposite.[/quote]

 

[aarhud]

Thanks all! Makes sense now.

 

[Simon Morgan]

TDS is NOT useful for determining whether your water is suitable for hard-water fish. Hard-water fish need Calcium and Magnesium (GH) for mineral balance and growth, and they need alkalinity (carbonate and bicarbonate) to keep the pH high. Water with salt (NaCl) added will have high TDS, but it may not have any GH or KH that the fish need. TDS is really more useful for softwater-fish, where you want GH, KH, and all the other ions to be low, and for brackish water fish that need a certain range of salinity.

quote="Simon Morgan, post: 79727, member: 799"] I honestly don't test for GH any more because using a TDS meter is quicker and cheaper. pH and KH are still important IMO for Hardwater species, and especially for keeping a healthy filtration system. IME it's easier for softwater species to tolerate hard, alkaline water than is for Hardwater fish to survive the opposite.

[/quote]

Gerald is correct of course, I wasn't entirely explicit.
If all the TDS in your water was made up of sodium chloride how would you know if you only used a TDS meter? It would not be suitable.
In practice, the TDS in tapwater mostly comes from Calcium carbonate, so as long as you establish that once you don't need to keep testing it.
For example if your tapwater has a gh of 6 but you have malawis you can increase the gh with buffers. I would use my TDS meter to check it because I know the base line gh and I know that the buffers I am adding mostly consist of gh.