Can't keep Magnesium stable with Kalkwasser

[Mcgeezer]

Need your help guys....

I run Kalkwasser in my ATO - Ca (440) and Dkh (10.1 - 10.2) are always consistent. 70g tank with 20g sump/Weekly 5g water changes with Reef Crystals.

However, my Mg reading always stays at 1185 even when dosing +weekly water changes. I’ll presume it’s one of 2 things:

1. precipitation
2. The coralline algae is drinking it up

My tank is mature at 7 yrs old and currently doesn’t have a heavy coral load, only some gorgonians, several sarcophytons, and a photosynthetic sponge.

Can anyone give me some tips on how to keep the Mg up consistently other than dosing? Or is this just something I have to deal with when running Kalkwasser?

 

[bertoni]

What are you dosing for magnesium and how much? That level is not that bad; 1275 ppm or so is the canonical ocean average. Coralline and other calcifying organisms will consume some magnesium, and Kalk doesn't provide any, so some supplementation might be needed.

 

[Mcgeezer]

I’m dosing with BRS Magnesium using their calculator. I really just want it to stay in the 1250+ range for my own sanity vs. daily dosing

 

[bertoni]

I'd try dosing and measuring after 10 minutes or so. Targeting 50 ppm for a first dose should give some margin for error. After that, 100 ppm or so is fine. How much are you dosing per shot, in ppm and ml?

 

[Mcgeezer]

I'd try dosing and measuring after 10 minutes or so. Targeting 50 ppm for a first dose should give some margin for error. After that, 100 ppm or so is fine. How much are you dosing per shot, in ppm and ml?

I try to do no more than 100ppm per dose

 

[bertoni]

Okay, I'd try measuring after 10 minutes or so, to see what's happening.

 

[Mcgeezer]

Well I figured out the problem...my BRS mag mix went bad due to age. I got a new bag today and got the tank to range on the first dose. I’m a happy camper!

 

[bertoni]

It shouldn't go bad, although it might have precipitated. Warming it should redissolve anything on the bottom, unless this is one of the "slushy" supplements.