Hi, Can anyone help me with my columbian sharks that are in brackish water, I have looked everywhere for advise and seem to be stuck Still with no answers they need a particular GH and instant ocean wouldn’t help or advise what their product contains as I’m not in the USA this includes how it increases the water GH, even though they sell it worldwide, no test kits can calculate saltwater GH apparently because of the salt content, they say it’s too high yet all over the internet they say columbian sharks are brackish then full saltwater but require a specific GH so it doesn’t make sense.
GH isn't useful in saltwater. Carbonate hardness (KH) which is the same as alkalinity for our purposes is widely used. What salinity (or specific gravity) is your tank?