How long for mag to come back down?

[Crush Coral]

I tried the trick of raising mag to 1500 to get rid of hair algae. Seemed to work for a while then it got resistant to the elevated level and is back. I have done about 8 30% H2O changes and it is still 1500. It took me forever to get it that high and now after not adding any mag for 6 months (I use Reef Crystals) it will not drop back down. My candy cane, rics and shrooms do not care for the high level. Will it drop back?

 

[HighlandReefer]

Magnesium is only used at about 6% of the amount of calcium that is used, so coral use it very slowly. Reef Cyrstals per Billy's tests run around 1450 ppm mag. So water changes using Reef Crystals are going to slowly reduce mag. Adding the fact that mag test kits are notoriously inaccurate as much as 200 ppm in some cases, I would say this is the reason why you are not seeing much of a decrease so far. Personally I would not worry about your level at 1500 ppm mag, since many hobbyists use Oceanic salt mix which runs around 1650 ppm mag per Billy's tests and no problems are reported by hobbyists who use Oceanic.

 

[Crush Coral]

Thanks, I am not worried about anything dieing but am unhappy with my candy cane which will not put out their tentilces and have not since I raised the mag. I appreciate the info and it does answer my ? as to why it is taking so long. Will just keep doing H2O changes.

 

[HighlandReefer]

Changing to a lower mag concentration salt mix will help.

Billy's reports on mag levels in commonly used salt mixes are found here:

http://www.reefcentral.com/forums/showthread.php?t=1714505

 

[Rwpdunne]

Just looked at the link for salt results i think he got the reefers best wrong mixed at 35ppt the ca410 kh7 and mg 1300 and that's using MN testkit Elos and FM