View Full Version : Who do I believe?

12/17/2010, 08:26 AM
Hi, I'm just getting started in the reef hobby and I noticed that the coraline algae was not growing very good. I tested for calcium and it was at 450. I bought a Salifert Mag Test kit and my water tested at 1100 which I read was low. I bought a bottle of ESV B-Ionic mag and dosed it per instructions. I dosed and tested every day for a week and the mag would not rise above 1200. I thought maybe the test kit was faulty so I bought an Elos mag test kit, checked my water this morning and it reads 1500 mag. I tried the Salifert kit this morning too and it read a little higher than usual, 1300. I'm using Instant Ocean salt at 1.025. Which kit should I believe. Thanks, Mozz

12/17/2010, 08:38 AM
You can go a little on the high side with mag safely. A real reading of 1400-1900 is fine. There is just no benefit in dosing heavy in that respect but it doesn't hurt anything.

You didn't mention your alkalinity and PH levels. Those are also key.

12/17/2010, 08:39 AM
I would try testing the instant ocean salt, it should be around 1300, it might give you a known value to compare the two test kits with. Have you tried testing multiple times? It could just be human error.

12/17/2010, 08:43 AM
It's impossible to say for sure which kit is correct without sending of a sample to a good marine lab.

The recommended level for mag is between 1250 - 1350 ppm. Higher levels don't seem to effect the coral much within reason. I would say your level is fine based on the results of the two kits. FWIW, hobby grade mag kits are notoriously inaccurate. I would concentrate on maintaining a relatively stable balance for your mag level using either of those kits. 200 ppm discrepancy in mag kits is not uncommon. Perhaps using the median reading between the two would be the best choice. ;)

It seems that as long as the mag level remains between 1100 - 1600 ppm it makes little difference to coral and coralline algae. High phosphate levels do cause problems for both coral and coralline algae.

12/17/2010, 09:05 AM
Thanks to all, my PH varies from 8.07 to 8.2. Alk 9. PO4 0.

12/17/2010, 09:32 AM
Your welcome. ;)

The water parameters you have listed look good.

FWIW, Randy provides a list of what the water parameters should be at in this article:

Reef Aquarium Water Parameters

You may find these articles interesting:

The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 1: The Salt Water Itself

The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 2: What Chemicals Must be Supplemented

The "How To" Guide to Reef Aquarium Chemistry for Beginners, Part 3: pH

The “How To” Guide to Reef Aquarium Chemistry for Beginners,
Part 4: What Chemicals May Detrimentally Accumulate

12/17/2010, 04:37 PM
Those numbers are all fine for coralline algae. I wouldn't worry very much. This calculator will show you how much supplement it takes to raise the magnesium level:


You probably weren't adding enough. It takes a huge amount of magnesium supplement to do much. I think the tank likely is fine as is, in any case.