Submerged Bio filter do I understand it correct?

Saltwater tanks also have a much lower bioload (or at least should), so not as much nitrifying bacteria is needed.

Biowheels are not a scheme, they do work very well because of the reasons described, more oxygen. Mut as long as you have enough aeration in the tank submerged medias get enough oxygen. Sometimes they simply need more surface for more bacteria because the bacteria are not working as efficiently as they would on Biowheels. I do not like the Penguins or the Emperors because of the cartdiges (not re-usable, include carbon, expensive, not that good at mechanical filtration). I do run a Biowheel Power Pro 30 on my 75. It is a powerhead hooked to a Biowheel, no cartridge. I wish they still made the Power Pro systems, besides on the magnum pro setups. And wet/dry systems such as bio-balls also expose the media to outside air like Biowheels.

The bacteria will live where it is best for them. This means the most flow where they will get the most oxygen and nutrients (ammonia and nitrites). This means they will colonize the media in the filters much more than that of the substrate and decorations.
 
I don't think the issue with a marine tank deals with the lower bioload..many have a reltively high bioload..once you consider they have very large 'clean up crew' coupled with a lot of invertebrates including corals, add in a few fish..some of hich get quite large
I think the bioloads are pretty comparable to fw tanks.
however, they do have high turn over, as mentioned, usually a minimum of 15X with as much as 30X
deep sandbeds, live rock and many use refugiums for filtration .adding in macro algae ..the marine tank can support anearobic bacteria add in macroalgae and they consume nitrates.

also if you use a ugf you have a very large biofilter in the substrate(if set up correctly)
 
I'll still keep bio-wheels in my scheme catagory.

For years, I ran tanks with nothing but ugf and powerheads with sponges on the intakes, and lots of flow/surface agitation. I occasionally polished the water with a Vortex and did plenty of water changes.

I agree that bacteria need air and food, but personally feel that is well dispersed through out a tank. Logic may lean that the increased food supply thru the filter would be a prime location for the bacteria, but I feel it is more evenly dispersed.

The bacteria are going to be where ever the right conditions are. They don't move to another area unless they die do to a lack of conditions and others grow in a more beneficial area.

Sploke, I feel that air contact is crucial and fully support wet/dry and sumps. I just do not see the bio wheels out there as adding that much compared to a large wet/dry or sump. Their advertising often implies that their use will give you a big bacteria colony, when it will only be as large as your bio-load and feeding habits.
 
To me, the real advantage of the bio-wheel is that you can actually replace the carbon / floss cartridge that most of these filters use without throwing away your entire biological filter. Yes its a gimmic, but its one set up so that when you keep throwing away what would otherwise be most of your biofilter, you still have enough lewft to protect your fish. You haven't thrown out the baby with the bath water.
In a much earlier era, we used to have air driven corner filters in any well cared for tank. To clean them, you would remove the filter floss and the carbon. If you were frugal you would try to re-use some of the floss but replace the rest. End result was that your filter was pretty much mechanical and chemical only. The "new" UGFs that came out at that time were the best thing a person could do because they didn't lose fish as often. They weren't throwing away the main part of their biofilter every few weeks. Now that we have power filters and canisters, most of us have learned to keep much of our media from one change to the next and not do a minicycle every time we do tank maintenance. The whole hobby has learned much since I started in it but the principles of biofiltration have not. We just understand them better now and don't follow such counterproductive practices any more.
 
That is true, bacteria load is dependant on bioload. But they will run more efficiently under certain circumstances, such in warmer areas (usually no different in our setups), or in high oxygen areas.

In many tanks there is a lot of flow throughout the tank, but there is usually even more in the filters (which create the flow). Since flow decreases VERY quickly once the water is returned to the tank the highest flow by far is in the filters. They will spread out, but the most will be where they do best, high flow (nutrients) and high oxygen.
 
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