Biological surface area in coldwater tanks

[AquaticEngineer]

So my second coldwater system already has a sump full of about 5 gallons worth of bioballs that stay completely submerged except for the very top layer.

 

I have room in the display tank in the false bottom that sits above the coolant coil to put more media in if I want to.

 

The question I have is should I go with dry tropical base rock like I did in my larger system or should I put more bioballs in?

 

This area has a closed loop draining underneath it so any sediment should flow through into the very bottom and get returned into the main water column. The area is accessible, if need be, by removing the large display rocks and taking off the false bottom cover plate. It would be a pain in the ass, but if I had to I could.

 

Or I could leave it empty. Its a pretty good sized area, its 15x 11x 6 inches, so I thought I should take advantage of the real estate and put more surface area in there.

 

Ideas? Thoughts? Suggestions?

 

Let me know if pics will help explain.

[C-Rad]

The danger with bio-balls is that if tiny particles of detritis are allowed to be trapped and build up in them, then you will end up with high nitrate levels as that built up junk breaks down. The way to avoid this problem is to have a mechanical filter (floss, sock, ???) that removes 99% of the tiny particles after they leave the display tank, but before they get to the bio-balls (plus rinsing the bio balls every six months to get the 1% that gets past the filter). I assume that water flows directly through the false bottom, so here's no way to do that in your set up, so anything (like bio-balls) that can trap particles is a bad idea down there. live rock rubble will have the same problem, but large pieces of live rock might be fine, as long as there's enough flow around them to keep junk from sticking to them (so you might need to add a circulation pump in there too). You also want to make sure that there's plenty of flow around the refrigeration tubing.

[AquaticEngineer]

Yeah the area I was thinking of adding some kind of media is a flow through tub that sits into the false bottom above the coolant cool area. The coolant coil has about the same area around it below this tub and it sits right next to the intake for the closed loop that runs to the fridge auto feeder.

 

The more I think about it the more a I think I will just take some of the tropical rock pieces that are in the false bottom in the big tank and transfer them over to the new setup. That will give me a chance to see what a few months worth of build up on the rock in the main tank looks like, and get some more of the established bacteria over.

 

Now I just gotta wait for my drill battery to charge so I can finish the upper false bottom cover plate.

[brandon429]

a need for more surface area is indicated by the presence of ammonia for a given bioload in an aged aquarium, that alone determines whether or not you need it in my opinion. the way I see it, any extra surface area not just bioballs presents nitrate issues due to accumulation, even items like ceramic and course media are worse than bioballs not because they are larger as a whole but have hundreds of times more surface area due to porosity. A great skimmer is a nice tradeoff to water change work sometimes.

[matt frizz]

Just remove the bio-balls. Useless detritus traps IMO.

[AquaticEngineer]

Just remove the bio-balls. Useless detritus traps IMO.

 

Anything is a detritus trap if you don't have adequate filter pads in front of it, a completely bare sump can be a detritus trap depending on water flow. What I'm trying to determine is if there is a better material to provide additional surface area in a coldwater tank other than bioballs.