Does dosing traces increase KH?

[Hydro]

Hi All,

Due to what I thought were signs of calcium deficiency (distorted and curled leaves) I have added crushed corals to my filter and KH has risen gradually from ~4-5 to 7 over about a one-month period (no traces were added during this time).

Last week, I resumed adding Flourish 0.25 ml twice per week for my 10g and have noticed a large jump in my KH from 7 to 15. It make sense since Flourish contains calcium. However, I'm not sure whether the amount I have been adding would be enough to cause such a jump. According to the bottle, 500 ml Flourish contains 0.14% calcium, which works out to about 0.00035 ml in each 0.25 ml of Flourish I added. What do you think?

I just want to be sure that it's not something else that's increasing the KH.

Thanks in advance.

 

[happychem]

Ca does not affect KH. KH is a measure of strong bases in your water, most prevalent: bicarbonate (HCO3-) and carbonate (CO3-).

Chelates would, in principle, have an effect, but I do not think that you would be dosing in sufficiently high quantities for them to increase your KH by 8mg/L.

 

[Hydro]

Thanks Happychem for the clarification. So KH measures only carbonate hardness (now I remember reading it, but just didn't register) and won't be affected by Ca even if you're adding CaCO3. I was suspicious of traces increasing KH given the small amount I have been adding, but thought I'd check with the folks here.

Hmmm ... now I have minor mystery on my hands. What's bumping up my KH so much? May be it's something I did inadvertantly. A large water change to reset things is probably a good idea at this point.

Thanks.

 

[happychem]

KH test kits don't only measure carbonate hardness, they measure alkalinity, which is the sum of all strong bases in solution, less the amount of H+. For around a pH of 7 in an aquarium where the sources of alkalinity are limited, KH and Alkalinity are approximately the same.

Phosphates, chelates, borates, silicates are all other possible sources of alkalinity; however, in most situations these are, even combined, negligible compared to carbonates.

A large water change or 2 are definitely in order. Keep track of KH daily over the next couple weeks (there should be another water change in there), it should be interesting to follow. I would expect it to creep up slowly from the crushed coral, drop at change, then back up. What likely happened in your case was a clump of ground up coral dumped into your water. How well did you rinse the coral in the bag before adding it to your filter? How much coral did you add?

 

[Hydro]

KH is back to 6 after water change. There's only a small bag of crushed corals in the filter and it was well rinsed before adding. The bag is still in good shape.

I'll be monitoring closely.

Thanks.

 

[happychem]

Great. Keep up with 50% changes weekly and you should see fairly stable KH values.