calcium/alk question

[tjm9331]

Hello everyone,

My 75 gallon system has been up and running since mid 2016, since then water changes have seemed to take care of replenishing what is used by the corals and system. I perform a 10% water change once a week.

Lately though I think my coral population has reached the point that I need to start dosing and this is where my question comes in. I have been testing weekly to gauge the consumption rate of each calcium and alkalinity. I've been noticing though that the only thing that seems to be used is alk.

Last test, calcium 420, alk 8dkh down from 9dkh

1. is this normal for alk to drop and calcium to remain constant? I would have thought that if the corals are using up alkalinity then they would be using up calcium as well. perhaps not at the same rate and my water changes are still keeping calcium in check?

2. is it ok for me to just add the proper amount of baking soda to my top off water to keep my alk stable?

I realize this may seem like trivial questions but this is new territory for me and I want to make sure I get it right before I go messing things up.

 

[mcgyvr]

Calcium consumption is not nearly as noticeable as alkalinity..
But its likely that its being consumed in the proper ratio..

Calcium consumption is approx 7ppm per 1dKH of alkalinity..

Many test kits aren't accurate enough to see that minor cal change but can detect the alk change..

I'd highly suggest a 2 part and not just alk concentration only..

 

[tjm9331]

Calcium consumption is not nearly as noticeable as alkalinity..
But its likely that its being consumed in the proper ratio..

Calcium consumption is approx 7ppm per 1dKH of alkalinity..

Many test kits aren't accurate enough to see that minor cal change but can detect the alk change..

I'd highly suggest a 2 part and not just alk concentration only..

Thank you for the suggestion mcgyvr, if I use a 2 part though wouldn't that then increase my calcium past 420?
Or perhaps my question should be how do I calculate how much to dose if I can't exactly figure out what my calcium consumption is or do I not worry about the calcium and just dose according to the alk consumption?

Would limewater work good as a 2 part?

 

[bertoni]

You could try dosing only alkalinity. The calcium is being consumed, as well, if the corals are using all that alkalinity, but the test kit probably isn't precise enough to see a change. Dosing both parts of the two-part should be fine.

In some tanks with low consumption, water changes are enough to keep the calcium level up, although I'm not sure that'll be the case for you.

Limewater supplies calcium and alkalinity in the same ratio as a two-part, so it's fine to use. It might be able to keep up with demand, although it is very dilute. It has the added advantage of not raising the salinity over time, and the pH bump might be useful, too. I would dose it with a peristaltic pump, though, either as autotopoff or metered, depending on how consistent the evaporation rate is in your setup.

 

[tjm9331]

You could try dosing only alkalinity. The calcium is being consumed, as well, if the corals are using all that alkalinity, but the test kit probably isn't precise enough to see a change. Dosing both parts of the two-part should be fine.

In some tanks with low consumption, water changes are enough to keep the calcium level up, although I'm not sure that'll be the case for you.

Limewater supplies calcium and alkalinity in the same ratio as a two-part, so it's fine to use. It might be able to keep up with demand, although it is very dilute. It has the added advantage of not raising the salinity over time, and the pH bump might be useful, too. I would dose it with a peristaltic pump, though, either as autotopoff or metered, depending on how consistent the evaporation rate is in your setup.

Thanks for the replies much appreciated, I think I'll try my hand at the limewater so long as you guys say it's safe to use without causing issues with my calcium.

I guess my next question would be how do I calculate how much limewater to add to my topoff?




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[bertoni]

You could start with 1 tsp per gallon and see how that goes. In theory, if you know the daily consumption of alkalinity and the amount of topoff water going into the tank, we could compute a better estimate, but it's probably not worth the effort. The limewater will tend to encourage coralline and coral growth by increasing the pH, so the estimate probably will be low, in any case.

 

[tjm9331]

You could start with 1 tsp per gallon and see how that goes. In theory, if you know the daily consumption of alkalinity and the amount of topoff water going into the tank, we could compute a better estimate, but it's probably not worth the effort. The limewater will tend to encourage coralline and coral growth by increasing the pH, so the estimate probably will be low, in any case.

1tsp per gallon of display water or 1tsp per gallon of top off? If it's display we're talking close to 65 tsp after displacement sounds like a lot lol but if that's what it is I'll take your word on it


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[homer1475]

1tsp per gallon of topoff. Not per gallon of tank water.



I believe(don't quote me as I haven't used kalk in a long time) the max saturation for kalk is 2tsp/G.

 

[Daddi0]

Lightly mix 1tsp of kalk per gallon of fresh R/O. Pour into ATO and let settle a bit before allowing it to pump in reef. Never let your ATO pump the bottom sediment.
Cheers! Mark

 

[bertoni]

I agree with 1 tsp per gallon of ATO water.

 

[tjm9331]

Thanks everyone, I ordered some Mrs. Wages Pickling Lime today and will start adding it to my next bucket of top off


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