The Complete System - I Want to Learn the Science in Water Quality

[Terrance]

I would like to learn the difference between FO vs FOWLR system. Are there really any extra benefit?

For a FO system, aerobic bacteria are developed in HOB/canister/media or even using 100% base rocks for both aerobic and anaerobic bacteria.

For FOWLR system, aerobic and anaerobic bacteria are partly or fully established on a porous rock from the sea/ocean. The "live" means that the rock comes with all kind of critters and organisms. Does these critters and organisms affect water quality? Are both FO and FOWLR system's water quality is the same?

This is just the beginning of the many questions I have.

 

[mojoreef]

Hello Terrance

Their is not alot of difference in the two systems you describe above. But their are a few, so lets first get the Live rock definition out of the way first. What hobbists call Live rock is basically dead coral that has been sitting on the bottom of the ocean for God knows how long, thus it is populated with bacteria and whatever else decided to crawl into or onto it or make it their home (hitch hikers) some folks tend to like it as it adds what they call bio-diversity to their systems, but with that you also run the risk of the nasty ones jumping onboard.

Ok so for the difference. In a system that uses bacteria as a form of filtration the bacteria will cycle through nitrogen based products. As you probably know one of the first forms of bacteria is the nitrifying bacteria that like to live in a more oxygenated zone (thus aerobic) they are followed by Denitrifying bacteria that prefer a more anaerobic zone. Soooo in your FO system you have a HOB filter, this is going to be happy holidays for aerobic bacteria but because of the highly oxygenated water that runs through it your kicking out the dinitrifiers. So this means that the end product of the nitrifying bacteria (Nitrates) will be produced and be let loose into the tank. Now knowing that dinitrifying bacteria like the areas that are more void of oxygen and thus live a litter deeper into the sand/rock how is that nitrate going to get to them?? thus the tank ends up ruing higher nitrate levels, which as long as they are not to high isnt to bad for hardy fish but can lead to algae growth.

Now if you take out that filter the nitrogen products are going to be taken up by the nitrifying bacteria in the rock/sand and they will do the same thing as the HOB. BUTTTTT the big difference is that the denitrifying bacteria are now directly below them (at hands length) and the nitrate is easily transported by the bacteria through the bio films they create to the dinitrifying, thus keeping the whole nitrogen cycle buried in the rock/sand.

As per the other critters that may inhabit the rock?? Well all critter only process 10% of what they take in and the poop out the other 90% so is their a big gain?? maybe a little

hope it helps


Mike

 

[Terrance]

Ok thanks Mike

If I put in 100% live rocks from the ocean, will it provide more "life" to a tank than a tank with 80% base rocks and 20% live rocks?
Over time does the "life" on the rocks slowly die? If yes, then how do we slow down the progression?

 

[Maxx]

Ok thanks Mike

If I put in 100% live rocks from the ocean, will it provide more "life" to a tank than a tank with 80% base rocks and 20% live rocks?
Over time does the "life" on the rocks slowly die? If yes, then how do we slow down the progression?

Terrance,
Yes, adding liverock directly from the ocean will add more "life" to your tank. However, as Mike stated, you also run the risk of other undesireable critters jumping on board your liverock. The list of these is lengthy...

Yes, over time, there is die off from the liverock. Some of it is desireable life forms, others not so much.

One way to replenish the life forms that die off is to get new live rock....this would obviously be expensive.

Personally, I prefer to start off with good base rock, and set it up the way I want, and let the necessary bacteria culture itself over time. This cuts the amount of hitchhikers down almost zero, however, I've found that most of the desirable stuff, IE sponges, pods etc, will populate on their own in time if the conditions are right.

These are not "immaculate conceptions" per se, but rather, they are brought in via water, and waste from critters you introduce to your tank....

Hope that makes sense...

Nick