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Re: Mulmming it over

> Doesn't mulm with all of it's bacteria contribute to eutrophication?

Sure, if you add too much. Adding a fair amount like a liter's worth to a 55
gallon tank's substrate and mixing it is going to help, not hurt a tank.
It's for the substrate, not for the water column so much.
> If you want to have much mulm you would have to have really
> good aearation of the top substrate for the bacteria to work
> really well and thus competing with algae?

I'm adding the mulm from the start to get the the gravel's cycle going well.
The organic matter is of use but mainly it's the bacteria I'm after. I want
that gravel to be as much like an established tank as possible, which
without replacing the gravel with old seasoned gravel, this is the next best

> I have recently added a spraybar at substrate level to spray
> aerated(?) water from the canister filter across the top of the
> substrate.
> Is this a good idea?

I spray the gravel horizontally from the back to the front of the glass
along the bottom.

I'm not concerned much about mulm build up on the top of the gravel. Some
folks have issue with that, I keep the tank pretty clean and the mulm never
bugs my tanks. I've seen it build up in other folk's tanks for various

I like to play around with various flow patterns in tanks.
> They contains a serious amount of oxygen demanding
> bacteria so the water from the pump should actually be
> oxygen depleted?

Sure. How much though? I don't think in the amounts we talk about that this
is a huge effect vs something like the fish population. The current provided
hopefully is enough to counteract this or else there's plenty of plant
growth and O2 produced.

> Is the surface-disturbance the only way
> a canister filter aerate the water column?

The way to aerate the water biologically is with plants or/and algae (and a
very few species of bacteria, not the ones we want).
That's been the focus/philosophy behind a planted tank, balanced aquariums
for the plants (and fish, those critters).
Since there's often excess O2(hopefully), adding a O2 consumer like fish etc
should be relatively balanced and most bacterial populations quickly adjust
to the load of the tank.

I suspect that the higher O2 levels amp the bacteria a good deal also like
it does the shrimps and fish. I suspect that may be a part of why the algae
does poorly.

Tom Barr