Do I really need a separate Bio-Filter?

[Luca Brazzi]

I know that I need Bio Filtration, however... consider this...

My 75 gallon tank is half filled with Lava and Tufa rock, and I plan to add more. With all that surface area on the rocks, might there be enough bacteria on the rocks themselves to support my Bioload all by itself? I have a 20 gallon sump with 4 gallons of Bioballs in it, and I plan to keep it but I was just wondering if anyone has tried this...

[OrionGirl]

That's the way that most SW systems run--rock and sand are used for the bio media. So, no, you don't need a separate filter for the bacteria to colonize, but you'll need to make the removal of the bio-balls gradual--a few cups a week. This will allow the bacteria on the rocks to build up to the needed size--right now, they are spread throughout the rocks and the bio balls, so removing the bio balls all at once will probably result in a spike.

[wetmanNY]

It depends on the bioload too. It'spartly a question of how many fish are in the system, their mass, and how much they are overfed. Successful "naturally" biofiltered freshwater aquaria generally depend on plants.

I overfeed my fishes. Who doesn't?

[Luca Brazzi]

I guess the main reason for relying more on the ornaments in the tank for biofiltration would be to eliminate the possiblility that a power outtage could destroy my tank. Currently, if the power were to go out Id have a problem because the biofiltration would be greatly reduced due to the fact that there is probably alot of bacteria on the bioballs that wouldnt be getting used to filter the main tank. However, if I slowly reduce the number of bioballs, this should force the bacteria to recolonize elsewhere (the rocks)... Theoretically.

The problem with this however is that lets say I reduce the number of bioballs, and can still maintain the current bioload. How will I know if the rocks in the tank can continue to maintain the load as the fish grow? According to the bioball documentation, each gallon of bioballs can sustain 40 gallons of marine life, I dont have any numbers on how much life can be supported by the rocks. I guess that Id just have to constantly monitor the ammo/nitrite levels.

[Cloud-9]

Well, if you have a power outage, the circulation in your tank will stop. The powerheads will stop functioning and the water won't circulate enough. If this continues for a long time, then it is possible that you will lose some of the bacteria on the rocks. Water movement usually helps to distribute oxygen around the tank. If you're really worried about power failure then perhaps you might consider a back-up power supply to run an air pump. I'm not sure if the automatic back up power supply used for computers will work for an air pump. I have not tried that approach. But perhaps you can try and time how long it can keep the air pump running.

[demon_surfer]

if you are worried about powerfilters goign out why dont you try and rig up the outtake and intake pipes to flow like the siphon tubes, if you can secure them to the tank and the sump it should work as long as you can get the water flowing and keep the ends in the water. you might have trouble doing this if the sump is sitting beneath the tank (which it probably is) but it coudl work and would reduce your reliance on electricity

[wetmanNY]

Is this the "endless siphon" perpetual motion machine, demonsurfer? Look at "The Museum of Unworkable Devices: at http://www.lhup.edu/~dsimanek/museum/unwork.htmThe first invention, Robert Fludd's "Closed-cycle mill" of 1618.