rock replacement

If I replaced 75#'s of my existing rock with Marco rock keylargo base rock, (in tubs 4 days) how bad would the cycle be? As everyone knows my tank is over 6 yrs old so it is very stable I have 170# of live rock now.

Edited by bugzme - July 05 2010 at 7:22pm

If that rock is like LBTR, and I think it is. Isn't it mined from the ground? Then it will hardly create any pollution. If I am right about this, you could do a lot of it.
I'm with Santiago on this. I don't work by pounds. I work by percentage. The biofiltration works this way. If you change out half the rock, that means you have cut its filtration in half. That's why taking it slow and doing it in portions over time is most often the better way to go, no matter how old the LR or the tank is. It's also a big job. Biting off smaller chunks at a time is easier, in my experience.

Just my 2 cents.


Edited by Mark Peterson - July 06 2010 at 10:29am

Mark Peterson wrote: The biofiltration works this way. If you change out half the rock, that means you have cut its filtration in half.

Yes, I too believe that, speaking in general terms, LS offers a greater percentage of filtration than LR, so I agree. What I meant was 50% of the biofiltration provided by just the LR component. My thought is that removing 50% of the LR would reduce the tanks biofiltration by 30%.

I agree with tCfab that the Key Largo rock may have a higher amount of PO4. This would create a pretty good algae bloom. Testing is probably the only way to know since I believe that Jeff has been keeping this rock in relative darkness, no?

It's had time to show in the water if PO4 was there. I'd say the rock is ready to go.

If it was me, I would put in 2-3 smaller pieces (~10 lbs.) and watch to see whether or not they get a brown surface algae growth. That would help me decide what to do next.

Great info, I was wondering the same thing ( Thanks )

No it's not bad, it's normal.
The amount of brown algae is what I would look at to help me choose how to proceed.
A tank with too little biofiltration, brown algae(diatoms and dino-flagellates) is going to be much thicker or more extensive than in a tank with sufficient biofiltration.

You may start to notice a green tint to the rock. This is a coralline algae that starts first. Next you should see dots of pink and/or purple coralline algae. Here is a pic of some LBTR at about 3 weeks:

Mark Peterson wrote: You may start to notice a green tint to the rock. This is a coralline algae that starts first. Next you should see dots of pink and/or purple coralline algae. Here is a pic of some LBTR at about 3 weeks: