Cannot keep DKH above 7

WoodsieFL · Feb 12, 2022

I’m having trouble keeping my dkh above 7.0. I’m currently dosing two part (80ml per day alkalinity) along with fully saturated kalk ATO into a high flow area of my sump. Does anyone have any advice? Here’s some tank details which I know you’ll have to know in order to help. Keep in mind my magnesium is right on the button at 1400ppm.

70 gallons total volume

10 gallon water changes per week with Red Sea coral pro salt

CO2 reactor with solenoid keeping ph at 8.2-8.3

Fully stocked with mid sized frags. It’s a mixed reef.

BRS 2 part system through an apex Dos

I’ve done the BRS adjustments with their calculator twice over and both times the dkh dropped down to 6.8 - 7.0. I’ve used two different test kits and Hanna checkers. I test in the last three hours of my 9 hours light cycle. As mentioned before, I currently have 80ml of Alk being dosed per day. Not too sure what’s going on here. Any ideas people?

Uncle99 · Feb 12, 2022

Your not dosing enough?

sawdonkey · Feb 12, 2022

Fully saturated kalk alone should be enough to make your alk rise to undesired levels…even without the two part. Is all of your topoff water saturated with Kalk? How are you adding the Kalk?

I have a tank packed with SPS and I don’t even fully saturate my topoff with Kalk and it keeps up with demand, so there’s something odd going on with your tank or your testy, especially since it would like you don’t have a high alk demand tank.

I’m not sure what to tell you except dose more and see if alk rises.

dedragon · Feb 12, 2022

double check with a second alkalinity test kit

WoodsieFL · Feb 12, 2022

If I dose more my Ph creeps up near 8.4 which isn’t what we want. As mentioned in my initial post, I checked with two different hanna checkers and a Red Sea kit. All say the same readings +\- .1

Waters · Feb 13, 2022

Do you have sand, and if so are you checking to make sure there aren't areas forming clumps?

WoodsieFL · Feb 13, 2022

Oh yea I definitely have some hard clumps in my sand bed.

Garf · Feb 13, 2022

WoodsieFL said:
Oh yea I definitely have some hard clumps in my sand bed.

I assume your alkalinity sup is a carbonate, if it’s sending your pH up. It may just be precipitating out in the sand. Try using a bicarbonate as this has almost no effect on pH. I would test every couple of hours for a day, just to get a handle on what’s going on. However, fully loaded kalkwasser topoff at 1% tank volume can achieve a lot and may increase your pH quite high also so a pH probe calibration would be first on my list. You got a pic of the tank?

polywise · Feb 13, 2022

Why are you running two part if you have a calcium reactor?

you need to use one or the other
I think that's why you are having issues.

WoodsieFL · Feb 13, 2022

Yea I’m running soda ash as an alk source. I will attach a tank photo for you. I’m not running a calcium reactor though I’m not sure where you got that from.

sawdonkey · Feb 13, 2022

WoodsieFL said:
If I dose more my Ph creeps up near 8.4 which isn’t what we want. As mentioned in my initial post, I checked with two different hanna checkers and a Red Sea kit. All say the same readings +\- .1

Most of us would kill to maintain 8.4 ph. I think you’re fine on PH until you start getting in to 8.6+…and even then, I’m not sure you’d see negative impact? I wouldn’t worry about that.

I would choose one dosing method, not two, and go with it so you can attribute its impact without obscuring it with the impact of the other. I like kalk, but others like two part. Choose one.

polywise · Feb 14, 2022

CO2 reactor with solenoid keeping ph at 8.2-8.3

sorry, thought you meant a calcium reactor.

In the past I have use baking soda to help raise DKH in my tank

Randy Holmes-Farley · Feb 14, 2022

I'm not understanding what you find if you increase the alk dose?

If pH is limiting, switch to a lower pH alk mix, such as using baking soda instead of the sodium carbonate.

If the precipitation of calcium carbonate (e.g., hard sand) is a problem, then here's my general recommendation:

1. Stop all efforts to boost pH.
2. Stop dosing alk for a bit and let it decline.
3. Reduce pH by switching to a low pH alk mix like sodium bicarbonate, or a calcium organic such as Tropic Marin All for Reef.
4. Ensure magnesium is normal to high.
5. Keep organics and phosphate on the high side.

After a few days of not dosing alk, restart slowly, adding additives to a very high flow area so it mixes in fast.