KH and PH issues in new 20 gal planted tank

[aquandry]

Hi all, hoping you can help me out. I have a new 20 gallon long tank that I'm cycling. It's got Miracle Grow Nature's Care soil with a sand cap. I've got a bunch of plants in there that I got locally. I have some dragon rock and a small piece of drift wood.

I live in New England. My tap water is extremely soft (maybe 1 drop each, if that, on the API GH/KH test kit) and is about a 7.2 PH. Before adding the plants I believe my PH was staying consistent in the tank and the GH/KH were both increased to whatever 2-3 drops calculates to (maybe due to the dragon rock?). I've noticed the nitrogen cycle seems to have stalled and my water PH is reading at the bottom of the API test kit scale (so 6.0 or below).

I've read dying plants can cause that.. but I've also read plants in general can pull minerals out of the water. I think there are some dead leaves in there, but I don't see anyting that is a big decaying mess (although I do have problems with the soil generating tons of gas under the sand still).

Should I be waiting to see if things stabilize more? Or should I be adding something? I was planning on adding some crushed coral, but I don't want the PH to go up to 8+... since I want to keep a community tank with Corys, maybe some tetras, and then either a Gourami or something else.

Any advice is welcome. TIA!

 

Edited February 14, 2021 by aquandry

[Hobbit]

Yep, you can put in a little crushed coral and it will be fine. Start with maybe a quarter or half cup if you’re nervous (I’m usually nervous 😄). It will dissolve a lot more slowly than wondershell so you’ll have a chance to observe how it affects the pH over time. Since you don’t have fish yet you have a chance to change things slowly.

I have very soft, acidic water out of the tap (pH 6) and I actually add a bit of baking soda (sodium bicarbonate) whenever I do a water change. I just do a quarter teaspoon per five gallons. Someone here recently pointed out that the sodium doesn’t really do anything for your aquarium, so you can also get some powdered calcium carbonate and use that instead. 

I bet you’re right and the plants have taken up whatever was keeping your pH high. It’s petty unusual to get high pH with low GH and KH, so I wonder what it was! Getting some carbonate in there will help raise the pH and protect against swings.

Beautiful setup by the way!

[Mmiller2001]

You could use GH boosters, they can be added directly to the tank. GLA and Nilocg are good companies. They contain Ca, Mg and some K. I like potassium carbonate for KH, won't affect GH and super cheap on Amazon. 

https://greenleafaquariums.com/products/the-ultimate-gh-booster-1lb-bag.html

https://www.amazon.com/dp/B00BPUTXGQ/ref=cm_sw_r_cp_awdb_imm_t1_WS6PJ1FXNWB4FJ0624E7?_encoding=UTF8&psc=1

Then use this calculator for dosing.

https://rotalabutterfly.com/nutrient-calculator.php

You could front load your minerals on water change day.