Why the need to top off soil with gravel?

[octopus]

I came across several set up with gravel top and soil bottom. Can someone share with me the benefit of this method. Currently i am using exclusive soil base but seem to be having some teething problem. Hopefully gravel top/soil bottom could offer some solution.

[zacks]

i used to top soil and the bottom layer using lava rocks as for bacterial house......

for me better the top with soil so Foreground Plants will be easier to absorb the soil nutrition.......

maybe someone could advise the better methode?

[Shadow]

depending on what type of soil do you use. If you are using Aquarium soil such as ADA, gex, magic soil, etc you do not need to put gravel on top. in fact it is encourage not to.

[aquarius]

I would like to add that you only use lapis sand or gravel to top up the soil when you're using those garden soil, otherwise you don't need to do so.

[flowerflower]

To add on, the type of plants and the size of grain of the soil might play a part. I currently planting HC, and the soil is too large a grain. Finding it hard for HC to root properly, especially if the fishes love to pick on them.