2-Part Precipitation Problems!

[ajnies]

Hello all,

I've been dosing 2-part in my systems for years with no issues... until recently. The past several months my tank has gone from stable one week to crazy alkalinity and calcium fluctuations the next with notable precipitation in the substrate around the rocks and near the waterline on the glass.

I've done loads of research and read several of Randy's articles, but can't pinpoint my issue. I've calibrated my dosing pumps, stopped dosing for several days to measure the drop in Alk (measured 1.3 dkH drop which feels high considering the tank is lightly stocked) and Ca only to restart the dosing pumps at the proper amount and have the levels continue to fall. I've programmed the dosing pumps to ensure they don't dose at the same time and even installed a small powerhead aimed directly at the spot where the dose occurs and still no luck.

My pH runs between 8.1-8.3, measurements are taken via Trident, and dosing is performed via the DOS (auto dosing is not turned on).

The tank is about 40 total gallons and has significant coralline growth, but only four small(ish) LPS corals at this time.

Any help would be appreciated!

 

[Randy Holmes-Farley]

What two part are you dosing?

 

[ajnies]

Dosing BRS 2-part as well as Balling Part C.

 

[Randy Holmes-Farley]

I'm not sure why you have precipitation now if nothing apparently changed, but once it starts, you need to break the cycle or it will keep going.

Here's my standard recommendation on how to do that:

1. Stop dosing alk for a bit and let it decline.
2. Reduce pH by switching to a low pH alk mix like sodium bicarbonate, or a calcium organic such as Tropic Marin All for Reef. Stop any outside air use or a CO2 scrubber.
3. Ensure magnesium is normal to high.
4. 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.

 

[ajnies]

Thanks so much for the suggestions!

As I mentioned my pH currently runs 8.1-8.3 throughout the day (probe was calibrated about two weeks ago) and I do run a CO2 scrubber. Without the scrubber my pH was hovering around 7.7-7.8. Everything I've read seems to recommend a higher pH range. Are you thinking the slightly elevated pH could be causing the precipitate?

I don't currently have any sodium bicarb on hand, but I'll pick some up. Would you suggest using this going forward? or only for when I restart dosing to avoid any large pH spikes when brining the levels back up?

My mag levels are averaging 1350, NO3 is 2.5, and PO4 is 0.04 would you suggest elevating any of these levels?

I also see you only mention turning off alk dosing, I'm assuming I should also turn off the Ca during this time?

 

[Randy Holmes-Farley]

Thanks so much for the suggestions!

As I mentioned my pH currently runs 8.1-8.3 throughout the day (probe was calibrated about two weeks ago) and I do run a CO2 scrubber. Without the scrubber my pH was hovering around 7.7-7.8. Everything I've read seems to recommend a higher pH range. Are you thinking the slightly elevated pH could be causing the precipitate?

I don't currently have any sodium bicarb on hand, but I'll pick some up. Would you suggest using this going forward? or only for when I restart dosing to avoid any large pH spikes when brining the levels back up?

My mag levels are averaging 1350, NO3 is 2.5, and PO4 is 0.04 would you suggest elevating any of these levels?

I also see you only mention turning off alk dosing, I'm assuming I should also turn off the Ca during this time?

Higher pH is better for calcifying organisms, but also causes more tendency for abiotic precipitation. It doesn't really matter if you turn off calcium or not. The calcium concentration is not the big driver. It is alk and pH.