Salt mixes and Carbon?


New member
Just wondering, wouldnt the regular use of activated carbon decrease the concentration of metals in our systems? Obviously some things are not removed, but things such as iron are, arent they?

Also, would you recommend one large water change, or several smaller water changes to either NSW or one of the "less toxic" brands of synthetic salt water?

Hi Alfred,

I really don't know how much carbon would help remove the metals. That could be determined by experimentation and testing (setting up some salts test for contents, filter them and then test again). Perhaps Randy or Habib could do this sort of testing, but I don't have either the $$ or the equipment to do it.

I did a major water change on my tanks to go to the less toxic brand and subsequently will just do water changes as usual.


Thank you for doing all of this work and sharing it with us.

I went back and read you earlier articles and if I understand it correctly heavy metals that are not exported in skimmate or algae may be bound or trapped in the live rock and substrate.

Are these things reversibly bound? If I change to the bioassay salt will the toxins leech back out? Since I do a 15% water change every 2 weeks, if they do leech out I could reduce the levels over time.

Thank you for your help.

Hi Derek,

The take home answer to your question is that I simply don't know.

In most cases, I think the materials are bound rather tightly and more-or-less irreversibly providing the pH stays in the normal aquarium/sea water ranges. If this is the case, than the materials would not leach back out into the water, but neither would their concentrations be reduced in tanks.

However, I really don't know if you could reduce the concentrations. On the other hand, it would seem that we could arrest the rate of accumulation.

Any observations when you tried the new salt? How did it mix? I plan on changing to the new salt and would be interested in anything you noticed.

I have been using IO for 8 years, but if this might prevent or extend the point where I have to tear the tank down I will be really happy to use it.

Thank you for bring this to reefers attention.


Originally posted by derek

Hi Derek,

Any observations when you tried the new salt? How did it mix? I plan on changing to the new salt and would be interested in anything you noticed.

I am sorry to say I can't be of much help. When I mix up a new salt water batch, I add fresh water to my mixing bin, and pour in some of the salt. I put a power head and then come back sometime later (10 min, 2 hours ... next morning :D) and check it with a hydrometer, and then I add more as necessary. I repeat this rather casual process over a day or two until the water is in the right range.

So... I didn't really notice any difference in dissolution rates. Now there may well be some, but I wasn't looking --- and so didn't see any.

I have been using IO for 8 years,

I had been using it for 11 years, and actually had used a much earlier version in the first cold water reef tanks I set up when I was teaching in Alaska in the late 1970s. The differences in survival with the various salts was surprising. I figured they'd all have poor survivorship... :D