Wet/dry Filters

[dfleary]

Why are wet/dry bio filters only recommended for freshwater tanks? Wouldn't they do just as good a job fostering denitrifying bacteria in a marine tank? (Is there something about the denitrifying bacteria strains in freshwater that requires more air contact?)

[Percula9]

Wet dry filters don’t perform denitrification.They only produce nitrates.You can use them in fish only marine systems.I don’t recommend them for reef systems.A sump would be a better way to go.Live rock and deep sand beds will perform denitrification.Water changes also to remove nitrates.

[dfleary]

Would a regular sump system (not wet/dry) be better, even for a fish-only marine system, or for that matter a freshwater fish-only system?

[mcgyvr]

A wet/dry is just one way to increase surface area for bacteria.

A typical saltwater setup will utilize sand and extensive porous rock to provide TONS of surface area for beneficial aerobic bacteria.
As such a wet/dry just isn't needed and as stated requires frequent maintenance to remove trapped particulate from its mechanical filtration before it breaks down further/clogs,etc...

A freshwater fish only tank will typically feature gravel and plants and maybe a few branches here/there.. As such it doesn't have nearly the surface area a saltwater tank would have and needs something to increase surface area for bacterial colonization..

[Michael Hoaster]

Wet/dry filters are perfectly good at what they do - converting ammonia to nitrite, and nitrite to nitrate, known as nitrification. The end result is a build up of nitrate, which can be addressed with water changes. Back in the eighties and nineties, this was state-of-the-art.

They fell out of favor when it was discovered that both nitrification and denitrification could be achieved with live rock and deep sand beds, where nitrate is further processed into nitrogen gas, which bubbles harmlessly out of the aquarium.

So wet/dry filtration is still useful for many situations, but most reefers choose the more complete solution to limit nitrate build-up. Plus, if you already plan to use rock and sand, it simplifies one element of a hobby that can get pretty complicated!

If you state your intentions, many of us would be happy to offer advise on the best filtration for your needs.