Low KH, high GH, neutral Ph??

[Wendy Knowles]

Hi all, I have just converted my 125g from artificial to real plants, and begun CO2 fertilization for the first time. I just tested my water, and am unsure what to do (if anything) with these parameters:

Nitrate 20
Nitrite 0
dGH 16
Chlorine 0
dKH 2.25
Ph 7.2 and stable
Ammonia 0

My tap water does NOT have this issue naturally, testing my tap water gives the following:

Nitrate 20
Nitrite 0
dGH 4.2
Chlorine 0
dKH 4.48
Ph 7.2

So why is my tank GH so high, and KH so low? I have no calciferous rocks or decorations, use regular old aquarium gravel with CaribSea Eco-Complete Planted Aquarium Substrate mixed in. I just added the CO2 yesterday, it’s the ZRDR CO2 Generator system that uses the baking soda and citric acid. My CO2 indicator still shows “low CO2, and no fish are looking distressed or gasping, everybody looking happy and healthy, and I just moved conservatively from 1 to 2 bubbles per second on my bubble counter.

Is the GH/KH something I need to worry about, and what do I do about it? Everything I read regarding high GH talks about using RO water, but since my tap water isn’t the issue it doesn’t seem to make much sense to go that route.

The tank is well established, it’s been running for 6 years, the only change is adding the live plants and CO2 over this past week. I do weekly water changes, treat all water with Prime, change out filter materials regularly, and use liquid Easy Green fertilizer, occasional Easy Iron liquid fertilizer, and Excel Flourish. Non-plant decorations are mostly resin, with a few natural driftwood pieces with Java ferns attached. Filtration is a PenPlax Cascade 1500 external canister, a Marineland BioWheel 150 and a Marineland BioWheel 350.

Do I need to with the GH/KH?

[Antichton]

I would expect GH/KH creep upwards if you are replacing evaporated water with tap water; over a long time period I would not be surprised to see GH go from 4 to 16 in this case.

It is curious that the KH did not increase in the same manner. Only thing I can think of that would lower the KH is algae metabolism or calcium carbonate precipitating out of the water since you mentioned you have no live plants. Maybe someone else has experience with this?

I wouldn't bother changing the GH/KH as long as it is stable and your livestock don't appear distressed. The only downside might be that if GH is very different in your tank compared to your LFS, new livestock might suffer osmotic shock without drip acclimation.

[Wendy Knowles]

Thanks! I do have live plants though. I previously only had two, and the rest artificial. Now over the past week I’ve been converting to a planted aquarium, and have dozens. The tank has almost no visible algae, and I actually  added new fish recently and they acclimated quickly with no issues.

It’s really strange, these numbers have me baffled! 🤷‍♀️