Alk climbs when no dosing

Shanet · Feb 9, 2019

My tank has had me scratching my head for the past few months, a bit of context.
I purchased a GHL KH Director for my tank some months ago, the tank is 180 gallons, moderately stocked with LPS (6 x 10 head Hammers, 2 x 20 head Duncan's, 2 x 4" Frogspawn, a small Elegance, a Goni and various Scollies and Mushrooms).
It has a crushed shell grit substrate about 3/4 inch thick and has been up and running for 6 months and has a light fish load (5 x 4" and 6 x 2" fish).
I measured my Alk usage over a period of a week and set my doser up to dose 2 part according to the usage. I then set up the KH Director to manipulate the dose up to 50%. All went well for a month but then the Alk levels started climbing and the KH Director couldn't keep them under control so I changed the amount dosed to half and let the Director take over again. It still continued to climb until the Director lost control so I stopped dosing all together and only measured.
The graph below shows the levels since I stopped dosing, they continuously rise then slowly fall. Can anyone explain to me why? Is it the shell grit? I set the Director for 8 dKH.

DSC reef · Feb 10, 2019

Bump, any members with the GHL KH director?

Ditto · Feb 10, 2019

@WWIII, @Marco@GHLUSA snd @Vinny@GHLUSA good to tag others

Are you doing any water changes, or dosing anything else or only the two part?

I had a brief pause in my tank last month not sure if it was the cold weather here in NYS but my tank dropped it aklinity consumption for about 3-4 weeks and went back up no idea why.

Mine is set for 7.2 and I have had to increase my dosing twice on my 3 part. When the KH can not keep up is a sign you need to increase the dosage on your 2 part.

When I see my KH not keeping up, my aklinity drops I increase my three part, rinse and repeat.

I only saw mine rise when I was doing awc changes if I was not dosing.

Shanet · Feb 10, 2019

quite the opposite, I work in a mine 2000 km away and only get home every 5 -7 weeks so thats when it gets a water change. The only other thing was that we had a heat wave recently with temps between 38 -49 Celsius, this is when it seemed to increase the Alk. I was dosing Red Sea part A & B coral supp.

WWIII · Feb 10, 2019

How much are you dosing? Are you using the BRS recipe or something else? I wouldn't think consumption would be very high in the tank as you describe it. How were you testing and dosing before the kh director? Also waterchanges and what salt?

WWIII · Feb 10, 2019

I see most of my questions answered there. It seems like it does pretty well for quite a while (2 to 3 weeks) based on your description and the graph above. Then starts to climb again.

How manl ml and how many times per day are you dosing?

Shanet · Feb 10, 2019

I'm using Randy's 2 part formula 1, NSW which is around 8dKH. Testing with Red Sea and Hanna egg. No waterchanges. I manually dosed for a week (without Director)

Shanet · Feb 10, 2019

Was dosing 4 x day @4 ml per dose

Shanet · Feb 10, 2019

then cut it down to 3ml per dose

Shanet · Feb 10, 2019

As you can see since I stopped dosing it still rises and falls 1-2 dKH. Could the shellgrit be melting/breaking down into buffer?

WWIII · Feb 10, 2019

Yeah that's basically very close to dosing nothing in a reef tank that size. Which is completely fine, but it shouldn't have much effect on dkh over that amount of time. I suspect something else is going on, I'm just not sure what? I honestly have no idea if the shell could be the culprit? I wouldn't think that would have any effect. It would have to be in a low ph environment probably to break down and increase alk. I wouldn't think it could absord alkalinity either.

Are your dosing heads calibrated and on the slowest speed?

Shanet · Feb 10, 2019

All the heads are calibrated and set to the speeds suggested by GHL for the Director, 2 part speed is Fast. Its almost like something was absorbing it and reached critical level and started releasing it. No probs I will ride it out and only start again when it gets below 8 dKH which is my target. Im about to set up a 600 gallon tank and was going to use the same substrate but now reconsidering in light of what has happened. I may even remove the shellgrit and see what happens.

WWIII · Feb 10, 2019

Shanet said:
All the heads are calibrated and set to the speeds suggested by GHL for the Director, 2 part speed is Fast. Its almost like something was absorbing it and reached critical level and started releasing it. No probs I will ride it out and only start again when it gets below 8 dKH which is my target. Im about to set up a 600 gallon tank and was going to use the same substrate but now reconsidering in light of what has happened. I may even remove the shellgrit and see what happens.

If it were me I would move the speed on the 2 part heads down to the slowest possible speed and spread it out to 2ml 6x per day. I seem to have much more consistency dosing a few ml at the slowest speed. I would try that and leave the kh director set how you have it. See how that goes for a bit.

Hopefully someone else will chime in on the substrate for ya!