When to change our carbon is a big unknown, too.
Alleopathy (chemical warfare) could be a factor.

i replaced my carbon every month and i am using premium carbon

Right, but how do you that it needs to be changed?

Alleopathy in corals is designed to be effective even in the vast expanse of the ocean. Another coral just needs to be down stream of another in order for the chemical to be effective. Never mind the dissolution factor.
How often do you put your hands in the tank?
How does that affect the corals?
What is the mix of corals that you have in your tank?
Maybe the mucous coating that corals shed has built up in the rockwork.

That could explain why Brad's new tank is experiencing good growth. No buildup of toxins yet.

Perhaps exchanging some corals with someone else would make a difference.

I'm just throwing out some suggestions, waiting for Hanna to come out with a test for toxins.:wink:

for me, nothing ever grew, even when the tank was new. It could have been a gypsy curse on that tank, for all I know :)

But my 75g and 150g before that grew stupidly fast, new and once running for years.

Hanna needs something to measure curses -lol

:pop2: Just tagin along here.... great topic :biggrin:

Right, but there are so many variables between tanks.

Age of live rock, how many corals, what type of corals, maintenance schedules, equipment, additives (or not).

Carbon doesn't work at 100% for 30 days then stop. It starts at 100% and gets filled up as fast as conditions dictate.
What happens as the carbon is filling up-the toxins have to go somewhere.

2 equal tanks -
1 with 2 corals, 1 with 50 corals. Both tanks have equal carbon changed at 30 days.

Too soon? too late? Who knows?:smile:

For carbon, I would think on average, it will be active for at least a few months (or you're not doing enough water changes :)), so changing it every 30 days errs on the side of caution.

But as with my tanks, everything is equal, same corals, fish, salt, schedules, etc, just the actual two tanks (disp and sump) are different. But very different results. Not to say it's the glass, but I've pretty much thought of everything else.

I actually have a thread about this problem posted a couple of months back.

http://www.canreef.com/vbulletin/showthread.php?t=65821

But how do you know it's on the side of caution?

Yes, I know..and you didn't reply.....:razz:

Have you ever seen any studies that glass could cause some problem?

Borneman cited a study that showed where removing a certain coral caused some significant changes in one tank. I'll try to see if I can find that.