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DIY methods for raising GH and KH?


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Here in NYC, my tap water is very soft: 0-1 kGH and 0-1 dKH. I want to provide ideal water parameters for livebearers, celestial pearl danios, rainbowfish, and other fish I haven't encountered yet that prefer harder water. I can raise GH by adding calcium sulfate and magnesium sulfate (which I believe are also known as gypsum powder and epsom salt, respectively). I can raise KH by adding baking soda. I plan to age my water in a barrel so that all the minerals that I add have time to fully dissolve.

Is that all there is to it? Does dosing some calcium and magnesium really make the difference between "my livebearers will slowly waste away in soft water" and "my livebearers will thrive because I added calcium and magnesium"? Are there other minerals that I need to add? My concern here is, am I optimizing for some numbers (i.e. the correct amount of GH and KH) without truly providing the right environment for hard water fish?

Edited by BenAquatics
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I also have pretty soft water and have had good luck with crushed coral. Personally, I put at bag in my filter, either HOB or canister, because I have black substrate and I don't like to see the little white specs. I've also used Texas Holey Rock, which I think is basically just limestone with similar results. Another thing that I've found that I think actually surprisingly well is seiryu stone. Apparently the white veins in the rock are also limestone.

All three of these get my pH up to about 7.6 - 7.8 range, and bump my GH up to about 150 and get my KH up to about 40 (still relatively low, but higher than it was before, for sure). Of course, take these results with as big a grain of salt as you like because (full disclosure) I am using the Co-Op test strips to measure all this and I find them to be somewhat unreliable.

However, anecdotally, I had good luck raising (and spawning) platies, mollies, swordtails and rainbowfish in the water with crushed coral and Texas Holey rock it in, so I'd say it's working.

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     I am from NYC as well, so I know your plight. I decided to start my livebearer tank before I knew better. Needless to say, my Mollies and Platies didn't thrive right out of the gate. I started doctoring my water, and noticed an immediate improvement in the overall behavior of the fish. I have adhered to the below for approximately 2 years now. Here's what I do:

1) For GH, I add wondershell to the tank, AND Seachem Replenish (or Equilibrium) each water change.

2) For KH, I add Baking soda each water change. In turn, it also raises my PH.

-I'll bring GH up from the tap of approx 40ppm to around 150-250ppm.

- I'll bring KH up from the tap of approx 25ppm to around 80-100ppm. In turn, this brings my PH up from the tap of 6.6-6.8, up to around 7.6.

Be careful with the baking soda. "Measure twice, cut once."


Edited by quikv6
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On 1/2/2022 at 6:17 PM, BenAquatics said:

Thank you everyone for the great replies! Based on your suggestions, I think I will experiment with crushed coral next -- it sounds like the least amount of work, and I prefer keeping things simple.

I'd recommend the coop crushed coral because it's just 1lb. Most other places you have to buy 10lbs.  If you're experimenting, 1lb is all you need. 

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