View Full Version : Why does 2-part dosing not work?

Yellow Eyes
10/02/2016, 06:36 AM
So I posted here around the beginning of the year. I was having a precipitation problem and I was dosing way to much BRS 2 part into my tank as a result. Luckily the worst precipitation occurred on my heaters, which slowly stopped coming on so much as spring and summer came around. However now my heaters are starting to come back on full swing, and a 2 part problem is presenting itself.

My levels have been stable all summer:
Alk: 9.5
Calc: 410
Mag: 1450 (I raised this value and maintained it to help limit precipitation)

Now my levels are trending downwards again. I wish I could say it is growth but I suspect it is not:

I dose alk at night (BRS 1.1ml dosers), after lights are out. 2 days ago I measured before it dosed, and after it finished, and saw a 1.2 dkH rise, consistent with what I have been seeing. I measured this morning, and saw only a 0.67 dkH rise, almost half! My alk was also ~0.4 dkH lower last night than it was the 2 nights previous!

What is going on? Why can I not seem to understand chemistry!? Any help would be appreciated

also: I have verified the ml/min of the pumps, still the same. I also now turn my heaters off 10 minutes before and after any dose to try and mitigate any precipitation on them.

Using Red Sea Coral Pro salt, measure alk with hanna, calc and mag with red sea

Martin Kuhn
10/02/2016, 06:55 AM
Tanks are changing consumption with better or worse conditions for your corals.

The better the overall conditions (especially N3 and PO4) at given constant and ok values for Ca, Alk and Mg, the higher the consumption will get.

Bigger corals growth (and thus consumption) can be more than the one of smaller corals.

I suggest to adjust the dosing to your tanks demand instead of being to much frightened from another precipitation

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10/02/2016, 08:14 PM
How much is going into the tank per day? I'd probably spread the dose throughout the day, rather than only at night. Also, the sodium bicarbonate version of the 2-part is less likely to cause precipitation.

I also agree that the demand might be changing over time.

Yellow Eyes
10/03/2016, 08:38 AM
Currently (and over the summer) I am dosing 60ml each of calc and alk. This is a 40g tank, 29g sump, I suspect around 50-55g of water volume total.

I was dosing them together over the entire 24 hour period (calc @ :00 and alk at :30) but I thought that would be too close and was causing precipitation so that is why I spread it out. Also to get the ph boost in the evening.

Yesterday morning, after dosing alk all night these were my values:
Calc: 410
Alk: 8.51 dkH

So I dosed ~20ml (according to BRS calculator) to get my alk to ~9, although I did not check as I got sidetracked.

This morning after dosing 60ml over the night as usual, my alk is down to:
8.12 dkH

So now this would require ~40ml of alk to raise this to 9.

Also looking further this is in the measurement error for the Hanna, so maybe I am overreacting at the numbers.

Either way it is still down.

Martin Kuhn
10/03/2016, 09:22 AM
Something around 8 is perfect for your alk. I wouldn't even target for 9

Keep it constant and do this independent from your ca level that you should keep constant at around 400- 420 .... you will see that this is perfect

Don not take care at all if consumption of alk stock solution (in ml) is higher (or even lower what I don't expect) as ca stock solution

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10/03/2016, 07:50 PM
60 ml is a lot of supplement for that size tank, if you are using recipe 1. I would consider switching to recipe 2 for a bit.

The need to space out the calcium and alkalinity doses is greatly overstated. I dosed 2-3 dKH of the part 1 supplement and the corresponding amount of calcium at the same time for years without problems. I was dosing into 29g tanks, so the supplements were spread throughout the water column very quickly, though.

Yellow Eyes
10/03/2016, 08:47 PM
I will try switching to recipe #2 and see what happens for a week or two and report back. Thanks!