Hi everyone. 5 days ago I started to cycle my 60P (17 gal) tank with ADA Tropica substrate, Eheim 2217 w/ Seachem Matrix, and CO2 (about 1/2 bps). I’ve been adding Seachem Stability per instructions since 4 days ago. I went ahead and added just a touch of CO2 because I wanted to observe my pH swings and there are a couple of plants in already. My tap water pH is 7.4, 2 degrees GH and 2 degrees KH. Tank pH ranges from 6.0-6.8, 2 degrees GH and KH, 1-3ppm ammonia. Daily 75% water changes drop ammonia to 1ppm and it goes back up to a high of 2-3ppm. Since last night, my tank KH started going to 0. I added 1/2 tsp baking soda last night and that brought it back to 2, and repeated that this morning. Right now (CO2 off), pH is 6.4-6.6. First question: what’s bottoming out my KH? Second question: obviously I need a better solution for raising the carbonate hardness. What is it? I don’t really want to use crushed coral, but another suggestion was Seachem Equilibrium. However, it doesn’t contain about carbon or carbonates - how exactly would it raise KH? They also make an Alkalinity Buffer which they market to “raise pH.” I get that raising KH will raise pH and I think that’s ok in my case...but I’d like to know what’s in it or by what method that raises my KH. I’d love to know others’ thoughts on dealing with very soft water and why the KH is going to 0 in my early-stage cycling tank. Thank you! (Also, I’m pretty decent at chemistry, biology, and complex explanations...so lay it on me if that’s your thing! I’m struggling to find details that go beyond “here’s how the nitrogen cycle works.”)

Your substrate is designed to strip the water of all KH. '

This is completely normal, I wouldn't bother adding any KH to the water as you would accelerate your substrate buffering lifetime.

Thanks. In the meantime, I've found out a couple of things. 1) Seachem Alkaline Buffer is "a sodium bicarbonate based buffer" - so is it basically overpriced baking soda? Cause I have a ton of baking soda. Any reason one would pay extra for this product?

2) I found this post from 2019 with a lot of sources supporting the fact that nitrification of ammonia utilizes carbonate. I read one of the scientific articles that gives the stoichiometric equation for ammonia nitrification:

1.00 NH4+ + 1.89O2 + 0.0805CO2 -> 0.0161C5H7O2N + 0.952H20 + 0.984NO3- + 1.98H+

This article suggests that I need to increase my buffering capacity or the nitrification process will stall. I'm not sure how to proceed. I'm also not sure why a substrate would be specifically designed to strip all KH, since that would result in pH swings from morning to night as the CO2 level changes.

As an aside, how in the heck does one use this forum?! Where can I find my post? I found it by going to "New Posts," but obviously that's not going to work for very long. I also don't get any notifications of replies to my post. Thanks for the help.

I's basically overpriced baking soda, you are correct.

Baking soda and potassium carbonate / bicarbonate can be used to increase KH and thus pH.


Sure, in a completely controlled environment that makes sense, however nature and our tanks are not completely controlled environments.

Take a look at a spring fed stream, full of decaying organic material. The water coming into the stream is extremely low in minerals and the humic acids released from the decaying organic matter is stripping what little KH there is out of the water, yet there is life thriving in that water.

ADA style aquasoils are designed to strip the water of all KH because plants prefer soft, slightly acidic water. pH doesn't fluctuate because the soil acts as a buffer in place of carbonates in the water. ADA fertilizers are alkaline so they are adding small amounts of KH to the water... but the soil quickly strips it away.

pH is supposed to swing through the day with CO2. Many of us swing our pH up to 1.4 from using CO2 twice per day, once when the CO2 comes on for the day, and once when it shuts off.

You'll have to look for the notification of a new post in one of your subscribed threads. You should also receive a notification that I quoted you in this post. You will receive notifications when someone tags you, quotes you, likes one of your posts or you get a PM. You can adjust your notifications in your settings as well.

Awesome! I subscribed to the thread (though I feel like users should automatically be subscribed to their own threads...). I did get the notification of the quote. Thanks for helping me out with that.

Thanks even more for the detailed explanation of what's going on with ADA soils and the KH. My pH only really swings from 6.0 to 6.8, so I guess I don't need to worry about it. I was trying to increase it to encourage the cycling; I was worried that I'm just starving the nitrifying bacteria with the low pH. I definitely need to study natural environments more...half the fun of this new planted tank is the chance to study a piece of nature right in my living room.

Thanks again for your help.