Deep Sand Bed and Biopellet Reactors what happens?

[allyourfish]

I am new to the scene of Biopellet reactors, but I am learning quickly. I am setting up a high tech 55 breeder with 20g custom sump. I plan to run ZeoBak, ZeoStart and ZeoFood, to populate my system and reactor. I am also setting up a minimalist aquascape with Pukani and need to build a frame to support some of the show pieces out of PVC, This PVC will need to be hidden under the sand bed to support this rock and I am assuming in order to cover the piping I will be needing nearly 4-5 inches of sand bed, (Possibly?) This has me questioning some chemical processes in my system. Please feel free to correct me if I am wrong at any point.

I understand DSB are in place for the reason of promoting anaerobic and aerobic Nitrifying and De-Nitrifying bacteria to enable your system to complete a FULL nitrogen cycle. I am not using this as a method to cut down on water changes (Just to hide pipes)... So If I am running an ULNS with a Biopellet Reactor hopefully keeping my parameters 1-2pppm Nitrates and .5ppm P04. In doing this. What will my sandbed do. Will my sandbed harbor many of the Nitrifying
(Ammonia-> Nitrite -> Nitrate) and the De-nitrifying bacteria (Nitrate -> Nitrogen) bacterias. Or will my sandbed hold the terrible so called Nitrate/Nitrite bubbles? If I start a biopellet reactor after months of my system being up and running with a DSB will it starve the De-Nitrifying bacteria in my sand bed, and a massive die off of these bacteria causing a spike of any sort? Or would the Biopellet dose the carbon (food) which would make up for the lack of Nitrates in the water? What am I in for? More importantly, What am I not understanding in this?


HALP :nerd:

 

[mcarroll]

Thanks to gravity and poop, your sand bed (like almost all) will be a detritus trap. If anything else contributes, such as over feeding, over stocking, et al, then it's going to be a serious maintenance chore IMO.

It's not impossible to make it work out, but what I've described is more likely. Sand beds like that (thick) are much better off in a separate tank where detritus can be excluded or controlled more easily. A thin sand layer (<=1") can be tolerated in a reef tank, but as you see from the experience of others, even that often becomes problematic, especially after a year or two.

Instead of creating such a situation, I would look for a better alternative to PVC for mounting your rock...fiberglass rod, acrylic rod or sheet and/or custom aragocrete all come to mind immediately, but I'm sure others could offer some ideas too!

Hope this helps!

-Matt

 

[ChristopherKriens]

I keep a moderately deep sand bed and run biopellets (both for 1.5 years). If you are running biopellets, the nutrient processing power of your deep sand bed is going to be comparatively minimal. The classical advice to not disturb the sand bed doesn't apply so much because the anaerobic bacterial population in the sand bed is there to a lesser degree and if they do get disturbed somewhat, it's fine as they're not crucial to the nitrate-processing path anyway.

Mcarroll is right in that it's a maintenance chore. With good flow and regular clean ups it can be done, and I think it's worth it– but if you see yourself getting lax in the future I would look to a different solution.

 

[allyourfish]

That's good news to hear, You are actually the perfect person to be answering my question Christopher. I just realized your tank is my inspiration for this build. Between the aquascape the mechanics. It's been a system I have been trying to build for quite some time. I am always maintaining my tanks, I'm up to 3 so far all being reefs. I am just wondering how to clean the sand bed effectively without removing extra sand?

 

[mcarroll]

I would actually remove some sand with every water change just to be sure you're thorough in cleanings. There's almost no other way to get the "fines" that drift down into the sand bed. A gravel vac will work on the open areas...not so much around rocks or under coral where most fine detritus gathers. Sand is CHEAP and detritus is BAD, so try not to worry about it.

-Matt

 

[ChristopherKriens]

Hah, that's flattering Some sand will inevitably end up in your bucket if you're siphoning thoroughly. Every six months or so I dump a new bag of sand in to replace what's been pulled out. You don't have to do this for nutrients really, but it's the only way I've found to really keep fine deep sand bed looking good.

 

[DaveMorris]

I never vacuum my sand bed because that is exactly what will prevent it from doing what it is there for. I firmly believe that if you have the proper assortment of sandbed fauna and critters your sandbed will not become a "detritus trap". It is correct that maintenance is critical for a sandbed to be beneficial as opposed to detrimental to a fish tank, but that maintenance can be handled naturally by the very creatures that live there in the wild. My current build is the first tank that I have used bio pellets on so it will be interesting to see if my methodology proves correct as I expect it to.