newb with nitrate question

[Actuarial Goat]

My plan is to begin my 125AGA with 2 Lifereef overflow boxes flowing to as large a sump as I can fit (feel free to check out my sump question thread;) The sump will have a 5-6" DSB and a lot of LR and a skimmer. Display will have 4" DSB and probably ~80lbs of LR.

My question is, if the sump and display LR and LS aren't enough to meet the filtration needs, can you add biological filtration to cover it? Say there's two more fish you want, but that would slightly overload the nitrogen-cycle abilities of the LR and LS. Can you put a HOB filter on the sump to supplement the "natural" filters, or would that screw up the nitrate-to-nitrogen-gas process in the live sand?

I've never done a display without a man-made biological filter. Maybe LR and LS are more than enough to handle a heavy fish load, IDK. Take it easy on me if this is a dumb question. Thanks.

[Playa-1]

I think you might want to up your liverock another 50-100lbs. I don't think a little HOB on the sump is going to cut it.

[D to the P]

Live rock generally is the predominant biological filter in a SW tank. I would use as much as you can, and if you're putting the sump under thank tank I'd use something like a 55 gallon tank. By the time your done you should probably have at least 150lbs of rock all together. But since you're putting a remote DSB and live rock in the sump, you mind as well go all out and just make it one big fuge. Plant some macro algae or some mangroves. They'll help remove nitrates and phosphates as well.

I'd also recommend a really good skimmer if you plan on having a large bioload. Something big.

[Actuarial Goat]

Thanks for these. I figured I'd put as much LR as possible in the sump, in addition to the 80lbs in the display. Playa-1, are you saying that's not enough?

I've considered a regular 55gal tank for the sump, those come cheap at the LFS. But it's too tall, there's hardly any clearance to get inside it once it's installed.

I'm hoping to begin as simple as possible. Can I plant macro algae directly in the sump tank, put a standard flourescent tube on it, and just leave it at that? And the heavy-duty skimmer was already planned, as this will be a FOWLR for as long as I can stand it, but eventually will begin introducing coral.

As to the original question, is there a fundamental chemistry reason why slapping an HOB Aquaclear or something like that on the sump is a bad idea?

[WaterKeeper]

The title of the thread is the answer. Adding a HOB will increase nitrates and not do much to enhance the tanks ability to handle increased bioloading. Trust in the Force my young Padawan. The natural filtration method you have chosen will work just fine. As for the rock, shoot for having 125 lbs total in the system.

[Actuarial Goat]

I figured that would be it, thanks WK.

Theoretical: If you had x lbs of LR and all was well, and you wanted to add additional bio strain to the system (more fish), could you add y more lbs of LR to accomodate? I know there are many factors that determine what a maxed-out stock for any one tank would be. I'm just curious if filtration winds up being the limiter on how heavily-stocked a tank is, or do you wind up ceasing to add fish for other reasons, before your filtration is ever maxed out?

Make sense?

[D to the P]

I would imagine there would be a time when the live rock to fish ratio would plateau out. But territory would also be a potential problem.

[WaterKeeper]

Makes sense but it isn't all that simple. You can add more rock but then circulation becomes a issue as the rock itself tends to block flow. You also increase contact point between the nested rocks and that decreases the all important surface area. The solution--it time to move on to a larger tank at that point if you want more fish. It is the difference in having a marine tank compared to a FW tank, where overcrowding is common and usually does no harm.

[Actuarial Goat]

Just looking for truth; that's what I wanted to hear. There is likely a point at which you want more than you can fit, and that's when it's time to accept it or break out your wallet.

Thanks again.