Increasing pH, Alkalknity, and Hardness in planted tank

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New Member
Oct 14, 2022
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Delhi, India
Hi friendly fish community!

We recently moved and began using reverse osmosis bottled water (because our new tap water is high in chlorine), which has slightly changed the water chemistry in our 20 gal freshwater planted tank.

My fish species include:
•Cory cats
•Neon tetras
•Flame tetras
•Cherry barbs

I read that Baking soda can help slowly increase these parameters, but that it can kill off plants.

My pH is 6.4, total alkanity is 20, and hardness is 125. I need to raise them back into comfortable ranges.

I live in India, and can't find Seachem's water conditioners anywhere, so that is unfortunately ruled out.

What are your favorite natural methods to solve this? Seashells? Coral? How do you know they're safe for fish?


Staff member
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Nov 28, 2006
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Teesside, UK
Baking soda is sodium hydrogen carbonate. It will increase pH and KH (which is a measure of carbonate and bicarbonate) but do nothing for GH as that is a measure of calcium and magnesium and baking soda contains neither of these.
Of the three, GH is the most important for fish so you need something that contains calcium and magnesium. Most people use something like Rift Lake Salts to increase GH, but I do not know what is available where you live, I'm afraid.


Supporting Member
Tank of the Month!
Feb 25, 2009
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A few observations. First, for the fish mentioned, there is nothing wrong with RO water. It is usually expensive, so the question is, why? Chlorine can be easily dealt with in a couple of ways, not least of which is using a good conditioner. There are better brands than Seachems, can you get the API Tap Water Conditioner? Or you can let the chlorine dissipate out in 24 hours before using the water.

There is nothing wrong with a GH of 125 ppm (I am assuming this is in mg/l or ppm). The KH at 20 ppm is OK. And the pH at 6.4 is perfect for these soft water fish. And these numbers will not cause issues for aquarium plants.

Do not use baking soda, this is not a permanent buffer (even if you did need one, which you do not).

For the plants,you may need a comprehensive supplement to provide all the necessary nutrients (there are 17). However, if the plants were doing fine before with or without fertilizer, the change in GH/KH/pH is not going to affect them.

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