Quote:
Originally Posted by michika
Mindy, how much overall water volume do you have? I see you mentioned the 90g, but I'm not sure if thats just the display or total system. My current water volume is 550g and I am not done adding onto this system. When I'm done I should have 1000g total. The costs really start to creep up at this level because you have to buy everything in such large quantities. How do you find the costs on dosing a system of your size?
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About 85-95 gallons net (that's taking into consideration water displacement from rocks and glass, etc.). In one year I use roughly: 5 kg calcium chloride, 8 kg sodium bicarbonate, 10 kg magnesium chloride. Fauna Marin comes in 4 kg buckets of each that I've seen for sale in the $50-60 per bucket range. So I use about $400 per year dosing. You're looking at 10-11x more volume than me plus or minus your actual amount of uptake, so that's really turning into quite a cost for you.
The BRS supplements are significantly cheaper and you can buy 5-gallon pails of the supplements. That's another option for you. I find I get better color and less algae growth when I use FM compared to BRS (particularly calcium and magnesium), but that's not a controlled experiment, that's just from switching back and forth a couple times and noticing small differences. I noticed similar differences when switching back and forth between IO and H2Ocean salt too. I also notice that the FM magnesium is less likely to become a solid block than the BRS magnesium which always got wet and rock-like on me.
FWIW, it takes A LOT of magnesium chloride to RAISE magnesium. It's not so bad once you've figured out how much you need to dose. Maybe you need to add a bunch to your waterchanges PLUS dose it on a doser. You mention calcium and alkalinity on a doser, are you manually dosing the magnesium? How much are you actually using?
Since I add 335 mL total Mg mix to my tank every 2 weeks, using the
Reef Chemistry Calculator I can figure out my tank is using "pretty much exactly" 100 ppm every 2 weeks or 50 ppm per week. Since you are using about let's say 30 ppm per day you're looking at about
3.6 kg of product PER WEEK for 550 gallons of volume. That's huge. I am guessing however, that this is a spurt in Mg uptake as others have already suggested.
Mess around with the Reef Chemistry Calculator both going forward and also reverse calculating to figure out how much you need to dose and see if you really are out of line or not. This calculator is really handy for figuring things like that out. FYI, the FM and the BRS Mg chloride are both "hexahydrate" aka MagFlake.
Here's a good article that explains where the Magnesiu is going. Keep in mind Randy Holmes-Farley wrote it in 2003.
Aquarium Chemistry: Magnesium in Reef Aquaria