The Planted Tank Forum banner
1 - 7 of 7 Posts

·
Registered
Joined
·
42 Posts
Discussion Starter · #1 ·
I recently revamped my 75 gal. with a heavy plant load. My pH was 7.6 with a kH of 5.

Those numbers were stable for a few days before I increased my lighting to 3 watts per gallon, began CO2 injection, and started dosing dry ferts. I've only done one day of macros (about 1 1/4 tsp total dry amount), and today I did the first day of micros (1/4 tsp).

Now, when I test, the pH is 6.8. That is expected, as I increased the CO2 with the lighting and ferts. But, the kH is now 7! I haven't done a water change or added anything else to the tank. Can that small amount of dry ferts cause the kH to increase by two degrees?!

Everything's fine, really. CO2 calculation is about 30 ppm. My drop checker is green. The fish are fine. I'm just wondering what would account for the increase in kH. :confused:
 

·
Registered
Joined
·
42 Posts
Discussion Starter · #2 ·
As I realize now, there are NO Carbon/Carbonate constituents in any of these ferts. That's what causes Carbonate hardness, Right?

So there shouldn't be any KH increase with the addition of ferts.
 

·
Registered
Joined
·
21,012 Posts
If you had done that by adding baking soda, it would have taken more baking soda than you dosed of macros to get that much KH rise - I forget the actual amount needed, but as I recall it would be around 3 tsp for that much water. KH2PO4 and KNO3, if that is all you dosed, wouldn't raise the KH at all. So, I suspect your substrate or any rocks in the tank are the culprit.

EDIT: It occurs to me that, while carbonates are what our KH is intended to measure, it isn't only carbonates that will raise the KH, which is actually the alkalinity that is being measured. I think phosphates will raise it too. If you made a mistake and dosed KH2PO4 thinking it was KNO3 you might have raised the KH some. (I could be wrong about this.)
 

·
Registered
Joined
·
42 Posts
Discussion Starter · #4 ·
... KH2PO4 and KNO3, if that is all you dosed, wouldn't raise the KH at all.
Agreed! I don't think it has anything to do with substrate/rocks, though, as I haven't changed any of that.

It's only one reading, of a parameter that's not terribly important. Anyway, I test daily, so I'll see what it is later.

I love my new Drop checker! :icon_roll
 

·
Banned
Joined
·
5,009 Posts
You may want to test your rocks, substrate, etc. with Muriatic Acid which is a dilute version of HCl. If it fizzes, you have a source of carbonates raising your KH. The carbonic acid formed from CO2 may be breaking down some of the carbonates in your aquarium that you didn't notice before you added CO2.

I like drop checkers too, but yours is a bit weird looking. :)
 

·
Registered
Joined
·
42 Posts
Discussion Starter · #6 · (Edited)
Possibly from substrate

... I like drop checkers too, but yours is a bit weird looking. :)
Hey! C'mon, my little drop checker thinks he's cute. I do believe you've hurt his feelings. :( It's not any weirder than expensive commercially available ones.



I hadn't thought of the higher pH (carbonic acid) being a cause (perhaps) of breaking down substrate. I haven't ever had that be a problem in the past with the same substrate; however, I also haven't had CO2 boosted up to maximum (with an accompanying -1 pH decrease).

FYI: I'm using mostly EcoComplete with a layer of quartz blasting sand.
 

·
Banned
Joined
·
5,009 Posts
Some bags of E-C can increase the KH.
 
1 - 7 of 7 Posts
Top