Help with Magnesium please?

[otrlynn]

I finally bought a Magnesium test kit online and used it for the first time last night. My magnesium measured 1200. My calcium is at 430. I am due to do a water change, and I will see if that brings it up to the recommended level of 1250-1350 per RHF in this article:
http://www.reefkeeping.com/issues/2004-05/rhf/index.php

If it is still a bit low, what do you recommend to raise it? Also, I have been having an ongoing mild/moderate problems with diatoms in the sand (nitrate is less then 1.0 and phosphates are not detectable, no hair algea etc). I read a posting in another thread where someone described a similar diatom problem which was significantly improved by raising magnesium levels. Any other opinions as to whether low magnesium can contribute to diatoms? Before someone suggests more flow, I have more than 20x turnover in my tank, more flow and I get sugarfine sand flying around...

[drparker]

This Reef Chemistry calculator Comes in very handy. I've used Kent Tech-M, Oceans Mag and now use Randy's two part recipe plus mag that I bought as a kit from Bulk Reef Supply. It's a lot cheaper that way. Heavy doses of Mg can also raise salinity so keep an eye on it while adjusting. I try to keep my Mg between 1300 and 1400.

As for Algae problems, Nitrates and phosphates will be used very quickly by the algae and might be higher than the test kits show. If you only have diatoms and no other algae problems I'd suggest adding something to your clean up grew to address it. Maybe some Nassarius snails and a cucumber.

[sassafrass]

My understanding of diatoms is that they require silicate to live ,both silicate and phosphate are ionically bonded to the hydrogen atom in the water. hence the need to de-ionize your water . You could check your TDS on your RODI output ,I would suspect your DI media is exhausted .
Lee

[otrlynn]

Thanks drparker. I am thinking about getting some more nassarius snails and perhaps a fighting conch (per someone's suggestion yesterday in a related post). I'm a little hesitant on the cucumber. I'll also try raising the Mag. a little and see what happens.

[otrlynn]

Originally posted by sassafrass
My understanding of diatoms is that they require silicate to live ,both silicate and phosphate are ionically bonded to the hydrogen atom in the water. hence the need to de-ionize your water . You could check your TDS on your RODI output ,I would suspect your DI media is exhausted .
Lee

TDS is 1 and I will change the resin this weekend. However, it just recently went from zero to one and the diatoms seemed about the same when the reading was zero. Thanks for the input. Lynn

[drparker]

Originally posted by otrlynn
Thanks drparker. I am thinking about getting some more nassarius snails and perhaps a fighting conch (per someone's suggestion yesterday in a related post). I'm a little hesitant on the cucumber. I'll also try raising the Mag. a little and see what happens.

If you don't go with the fancy colored ones you don't need to worry. I have two tanks and got two brown ones in questionable shape and a 4 hour drive. They didn't make it. One spit his guts day one and the other day three. They caused no issues with my tank at all even though it took me several hours for one and overnight for the other to get them out.

I've since got a healthy brown one from a LFS in my 75g that is doing great.

[Sk8r]

I dose mg with Tech-M. You should keep mg at 3x the desired calcium reading: ie, if you want a calcium level of 420, you want mg at 1260-1300. It does get used, apparently, and the level will sink, so setting it a little higher is fine.