The only advantage is the lower redox values making something(nutrients) more available. This can occur in the microsites on a porous grain of substrate without disturbing the bacteria.
Even if the gravel is moved around, the grain still stays the same.
The roots produce O2 around the active growing region.
Placing nutrients into the gravel vs the water column is not going to raise the O2 levels, it would lower them. Growth would be slower/similar, not slower.
Growth, or primary production is sometimes measured via O2 production/evolution. So if growth is slower, then there will be less O2.
There's some of the water column and some of the substrate nutrient sources going on in every nice rooted plant tank.
You need both, iron is very particular to have in both locations.
You can use macro's in the substrate but this has been going on for decades with soil(pre soak it for 3-4 weeks to remove the NH4), other things like osomocoat etc. Changing to non NH4 urea based products may help the initial set up, but the long term growth still demands a source of nutrients, you will need to resupply nutrients and wait till the roots grow over to where they are placed.
There is no such wait nor internal transport needed for the water column.
But if you think about like this, this may resolve any differences you and others might have about this issue:
__Let the plants decide__, provide both locations for the macro's/micro(without any NH4 except from fish), crank the hell out the CO2 provide even moderate light and do your water changes, pruning etc.
Fish waste is enough to grow most algae.
How do you plan to put that into the gravel?
If you really want to look into this dynamic, I have some papers to consider reading and also some methods you might want to start with first, RFUG and plain old sand makes a nice baseline to compare with since it does grow plants well when dosing the water column.
From there, you can add different things to the substrate(macro's NH4, jobes, iron only), flow rates(fast, medium, slow, very slow, none) etc.
Regards,
Tom Barr
Regards,
Tom Barr |