triguy Posted March 29, 2021 Share Posted March 29, 2021 Hi, I've been doing some reading about GH and osmoregulation and I'm a bit confused about the role GH plays in water. Could you put a brackish fish like a figure 8 puffer in high GH water (e.g. 12-20 dGH) and have them thrive as if the water was brackish? Thank you Link to comment Share on other sites More sharing options...
Biotope Biologist Posted March 29, 2021 Share Posted March 29, 2021 Hey no worries for the mix up. It does get confusing when people switch between calling gH salts and calcium and magnesium. Salt in chemistry just refers to any chemical compound with a cation of a base and an anion from an acid. This confuses even first year chemistry students so don't worry about not understanding what they mean when they use salts interchangeably with say sea salt. Sea salt is sodium chloride with some trace minerals that are dissolved in seawater such as zinc and potassium. So in layman's terms. General hardness just measures calcium and magnesium which some fish especially saltwater and brackish fish need. Specific gravity is the measurement people use for brackish and saltwater. This scale ranges from 1.000 to 1.032 for water and measures how dense the water is compared to a standard, in this case freshwater with no salt. As you are likely aware saltwater is more dense than freshwater so it will weigh heavier on this density scale depending on how much dissolved salt is in the water. In this case I am referring to salt as the common sodium chloride or table salt. 2 Link to comment Share on other sites More sharing options...
triguy Posted March 29, 2021 Author Share Posted March 29, 2021 Thanks Biotope that helps a lot. So if I'm understanding you correctly, you could put a brackish fish in a high GH environment successfully because their osmoregulation needs are met through the high GH. In other words, it's the GH needs of the fish being met that is important to them, not the density of the water; is that correct? Thanks again Link to comment Share on other sites More sharing options...
Biotope Biologist Posted March 29, 2021 Share Posted March 29, 2021 Typically they require high kH, gH, and pH. Brackish water fish do need some seawater in their environment, but it appears to be hotly debated as to how much. For example, bumblebee goby seem to live fine in specific gravities as low as 1.003-1.005. For reference saltwater typically measures in my area 1.024-1.032. Figure 8 puffer also require low-end brackish setups. For them I see people using specific gravity 1.003-1.008. Having that been said. To maintain the health of your fish, it is best to replicate the environment they come from. Figure 8 puffers come from river deltas in the mekong.These are a marine fish adapted to the stresses of freshwater exposure. Some seawater is required for their overall health. I would buy a gravity meter and see how much seawater you will need to maintain a minimal specific gravity. Keeping a figure 8 puffer in a specific gravity of 1.000 or lower will cause long term stress to the fishes kidneys and gills and reduce their lifespan. 1 Link to comment Share on other sites More sharing options...
triguy Posted March 29, 2021 Author Share Posted March 29, 2021 Thanks again Biotope. If you don't mind other questions... When you say seawater above, you mean some form of saltwater, correct? meaning water with a specific gravity above 1.000? Secondly, what is it that causes stress to the fishes kidneys and gills? Lack of salt or calcium or magnesium or some others? Thanks for educating me. Link to comment Share on other sites More sharing options...
Biotope Biologist Posted March 29, 2021 Share Posted March 29, 2021 Hey no worries. I would love it if more people got into brackish water tanks. They are quite fun. When I say seawater I do mean saltwater. You can either accomplish this by buying marine salt from a fish store or if you have a local marine fish store they sell saltwater by the gallon. This stuff is the best as it is purified seawater and already has all the trace minerals your fish want. Brackish puffers possess unique cells in their body that allow them to maintain salt ion pumps along their gills even in the absence of salt (sodium chloride). This is what helps them to survive in freshwater for extended periods of time. However, it is not indefinite. So to answer your question the stressor to their gills and kidney is the lack of salt in the environment to maintain their sodium ion channels. Although they do need calcium and magnesium for other biological functions. 2 Link to comment Share on other sites More sharing options...
triguy Posted March 29, 2021 Author Share Posted March 29, 2021 Perfect, thank you for explaining it all so clearly. It's very difficult to find accurate scientific information in layman's terms! Link to comment Share on other sites More sharing options...
Eric R Posted March 29, 2021 Share Posted March 29, 2021 @Biotope Biologist, I just wanted to add that I'm very impressed with the quality of your responses!! Link to comment Share on other sites More sharing options...
Biotope Biologist Posted March 30, 2021 Share Posted March 30, 2021 I'm glad I coud help ☺️ Link to comment Share on other sites More sharing options...
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