Easy question for researchers if I remove the up-take tubes of my under gravel filter and add some gravel will I have a plenum based substrate (plenum meaning a space of air) and will this space of air provide a satisfactory environment for beneficial bacterium?
Under gravel filters are really a thing of the past due to issues like high nitrates and trapped waste. Beneficial bacteria generally colonizes best on porous objects.
has me suddenly thinking, ... undergravel filter, doesn't have to fill the tank, ... i think is an excellent mechanical and biological filter ... there may be side effects, but should be great for getting floaties out of the water column
I don't think air is a suitable environment for the bacteria.
Canister filters provide excellent mechanical and biological filtration. I would most certainly not put UGFs in the excellent category along side canisters.
i agree with jaysee about air
in our world (we walk, live & breath in air - well standing on the ground)
yes, fish tanks can have problems, ... but not with mold, or fungus or that kind of stuff that can be really dangerous which is really easy in air environments, ... to humid, not enough fresh air flow, ... on it goes
worst i know of for aquariums is cyano, and as much of an ugly eye-sore, doesn't sound particularly dangerous (not an absolute, just for stories i've heard)
Thatís a good point about air and is indicative of my failure to communicate well. There is of course no air trapped under the filter plate. I used the phrase Ďair spaceí to describe the empty space between the underground filter plate and the bottom of tank. This empty space contains a lot of decomposing matter so will this break down of matter release stored carbon & nitrogen creating the necessary environment for bacteria colonization. This space might be low in dissolved oxygen saturation and allow the completion of the nitrogen cycle.
i do not think an undergravel filter will get that low i O2 to be considered anoxic (without free oxygen)
options to consider for such anoxic activity to complete the nitrogen cycle...
Deep Sand Bed (DSB) about 4+ inches of sandy substrate, typically 6" (do some research on this, i'll send you a PM on what site to look at)
lava rock (for freshwater) coral rock for saltwater) who's surface can colonize with bacteria that will gobble up available O2 till farther inside there is once more no available free O2. images that come to mind are those fine pored red lava rock pieces ... go with the same weight of lava rock that is typically suggested coral rock for saltwater ... i do not think this is as fine as the coral rock, so results will likely vary.
you could use the coral rock in freshwater but unless your pH is high it's going to slowly dissolve. then it no longer has sufficient depth to allow that deeper anoxic area to complete the nitrogen cycle.
You are most likely correct about dissolved oxygen levels.
What do you do when lava rocks floats not for just one hour or one day or one week but months?
My lava is from Mt. St. Helens and Spirit Lake. I was living about 45 miles north-west of the volcano when it erupted back in the 80ís.
if it floats, ... hmmm, all i've got is guesses
there may be completely sealed off air pockets inside
or boil it to induce the almost (but not quite) pockets to take on water
otherwise i have heard it's a bad idea to boil rocks for the risk of exploding (not joking, there are stories of people who have boiled rocks and found they turned into similar to exploding grenades in their kitchen.
so if they're still floating after many days, ... best to avoid that one.
that's what I understood
I remember the marine jaubert system which used a plenum also. It was supposed to provide the anaerobic/anoxic area for bacteria to reduce nitrates. and was very popular a few years ago (like 2000 or so).
Studies showed that nitrates were basically the same with or without the plenum.
IMHO undergravel filters do work to encourage the forward bacteria cycle. Just as wet dry filter do also.
Combined with plant filters like algae turf scrubbers, plants, refugiums with algae or even bio wheels you can complete the cycle nicely while returning oxygen to the system and consuming carbon dioxide.
So I find no need or use of a plenum.
I would much rather have a ugf especially a reverse flow UGF with plant life.
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