Why no filter under substrate

[Bad Inferno]

Why don't I see people recommending undergravel filtration....

I would have thought that it would be difficult to keep the substrate in good condition (alive) without some sort of water movement through it. ?

I was wondering those that recommend no under gravel filtration change their tanks often thus never end up with a tank >2 yrs old.

rob

[Roy]

I havent used UGF for years.
Got heating cable under the substrate so that creates water movement, also a decent cannister will keep the flow going and remove a lot of the suspended waste.
If you vacuum the substrate at water changes you will also get a lot of the gunk.
Well thats the way i do things and it seems to work ok.

Roy

[ILLUSN]

UGF can pull nutrient from the substrate into the layer of water under the filter plate, also in this same here there is no substrate for the roots to make contact with and so can lower their abitilty to absorb nutrients (some roots need substrate contact to develope the fine root hairs for nutrient uptake). heating cables, gravel vaccuming are ways to keep a slow movement of water through the substrate as are other more complex methods such as this http://www.aquagreen.com.au/files/Aquagreen_Plant_growing.pdf

I agree that movement through the substrate is important in long term planted tanks, but the only plants i've managed to grow well with UGF are Hydrophila sp. and elodea.

heres a page that proably explains it better

http://www.thekrib.com/Plants/kelly-intro.html