When to dose Ca and Mg?

RocksNStuff · Apr 28, 2021

Hi all,
I recently started testing for kH, Ca, and Mg. I test once per week and only have 3 weeks of data logged. My Ca, Mg, and kH numbers are trending down but still within normal range.

Ca: 420ppm
Mg: 1350 ppm

My question is: should I start dosing to maintain these levels or let them drop, then dose? Or get more data, then decide?

Thanks,
Luke

TexanCanuck · Apr 28, 2021

That's a very hard question to answer without a better understanding of what's in your tank. Can you please provide us more context?

How long has the tank been running?
What livestock do you have? Fish? Corals?
What are your longer term objectives?

RocksNStuff · Apr 28, 2021

P.s. I only have soft and LPS corals in my 75g tank. (And fish)

RocksNStuff · Apr 28, 2021

TexanCanuck said:
That's a very hard question to answer without a better understanding of what's in your tank. Can you please provide us more context?

How long has the tank been running?
What livestock do you have? Fish? Corals?
What are your longer term objectives?

All good questions!

I have LPS and soft corals and don't have any plans to have a serious SPS set up. Maybe a few of the easier ones here and there.

I have 2 clown fish, 2 damsels, 2 watchman goby, shrimp and snails.

I'll probably add more schooling fish and maybe a tang eventually.

mdb_talon · Apr 28, 2021

I prefer to keep some stability with the alk especially. So while anywhere between about 6 and 12 could be considered "normal range" you dont want it bouncing between that range between water changes.

I try to keep it between 8.5 and 9.5. If it starts dropping below 8.5 between WC that is when i start dosing on a new tank i setup. Calcium and mg i usually just dose once a week/month respectively when the tank is newer and minimal uptake. As growth/stocking level of LPS/SPS increase i increase dosing or frequency of dosing to keep up.

In your tank it is the LPS(and possibly coralline) that may end up driving you to start dosing.

There really is not a one size fits all answer, but if your dkh has dropped only a small amount in three weeks i would say you dont need to dose yet. If it has dropped from 11 to 7 though both are within" normal range", but i would say it is time to start looking into dosing.

RocksNStuff · Apr 28, 2021

mdb_talon said:
I prefer to keep some stability with the alk especially. So while anywhere between about 6 and 12 could be considered "normal range" you dont want it bouncing between that range between water changes.

I try to keep it between 8.5 and 9.5. If it starts dropping below 8.5 between WC that is when i start dosing on a new tank i setup. Calcium and mg i usually just dose once a week/month respectively when the tank is newer and minimal uptake. As growth/stocking level of LPS/SPS increase i increase dosing or frequency of dosing to keep up.

In your tank it is the LPS(and possibly coralline) that may end up driving you to start dosing.

There really is not a one size fits all answer, but if your dkh has dropped only a small amount in three weeks i would say you dont need to dose yet. If it has dropped from 11 to 7 though both are within" normal range", but i would say it is time to start looking into dosing.

Yes, I forgot to mention that my kH has gone from 12 to about 8.5 in that time. Sounds like I should dose?

mdb_talon · Apr 28, 2021

If it were me i would start yes. Others i am sure would disagree though lol. It wont be a lot at all initially and maybe it it just a ml or so every couple days....but trying to keep it as stable as you can is a good thing.

reefpaddy · Apr 28, 2021

Depending on size and quantity of LPS, regular water changes maybe all you need to maintain acceptable levels.

Gtinnel · Apr 28, 2021

If they are at levels that you want I would start dosing, the more consistent these values (mostly alk though) are the better. Since you have been tracking your usage it should be pretty easy to use a reef calculator and figure out about how much you'll need to dose. Once you start dosing, if you use dosing pumps it becomes a very easy task. Plus since your usage is low after you get it dialed in you wont have to mess with it for a while. I only dose 40ml a day and I only have to fill my containers up every 40 days.

RocksNStuff · May 3, 2021

Hi all. I tested again and my Ca and Mg are steady but the kH is dropping still. Is that possible? Or do I have test error....??

mdb_talon · May 3, 2021

RocksNStuff said:
Hi all. I tested again and my Ca and Mg are steady but the kH is dropping still. Is that possible? Or do I have test error....??

Alkalinity is much more noticeable because there is less of it. If it is dropping slowly it will be a long time before there is a significant drop in mg. Calcium is a little more noticeable, but still wont see big drops if your alk is only dropping slowly.

RocksNStuff · May 3, 2021

Ah. Good to know. So is it possible to dose kH alone or should I do Ca and Mg too?

tritonpower · May 3, 2021

I use BRS 2 part to dose plus tropic marin part C (covers mag). The BRS calculator is great as you can dose precisely. I started out dosing these by hand initially to get a sense of need. Check levels weekly. Once it is clear the need is enough for a doser then get actual dosers. If the need is low enough consider just dosing by hand once or twice a week initially. The levels won't be as stable as daily dosing but watch your corals and be sure they grow appropriately.

Fennel · May 16, 2021

RocksNStuff said:
Hi all,
I recently started testing for kH, Ca, and Mg. I test once per week and only have 3 weeks of data logged. My Ca, Mg, and kH numbers are trending down but still within normal range.

Ca: 420ppm
Mg: 1350 ppm

My question is: should I start dosing to maintain these levels or let them drop, then dose? Or get more data, then decide?

Thanks,
Luke

Do whatever you want as long as it is safe. I am still cycling a tank though and at the pet rock stage and haven't commit to having stable parameters when I can dose soda ash, calcium chloride and epsom salt right now whenever I want just to have a clean pet rock.. and am still waiting to see if anything sprouts.. best part of the whole hobby in my opinion, so far.. even steady parameters in this tank is too much stability and commitment.. cathartic.. when it comes down to the matter of fact and follow directions, I am lazy, but I will eventually get around to it..