After doing alot of reading online, I'm wondering if there can be any negatives to having too much LR's in the refugium?

If all I wanted, was nutrient export and stabilize water conditions. Would there be any negatives to having the following in the refugium, and what needs to be altered to make it more effective?

1. 3 inch sandbed(Limited by design of the CPR HOB)
2. as much LR can fit in the middle chamber.
3. baseball sized clump of Chaeto Macro Algae.

I don't think that you can have too much LR. If you need LR rubble to fill the compartment I am really pleased with the rubble that I got from Marco Rocks for in my sump.

Thanks Carmie

I was just surprised how many people on RC thinks LR does not have enough surface area to be effective at filtering. I can certainly understanding using rubble instead of rock for space constraints, but not sure why some people thinks it would be counter productive and ofcourse, DSP seems to be not a good idea there either.

Well, CPR aquatics seems to think 2" is enough on their support forums.

Aside from aesthetics a 3 inch sand bed is going to be of little use for nitrate reduction. If you're plan is to fill it with rocks then I think I would leave the sand out. Part of the problem with filling it with rocks is the flow through will very slow creating a detritus trap, and possibly leading to higher nitrates in the future. You could clean out the detritus periodically to avoid this.