[MattS]

http://www.plantguild.com/html/spot_fertilization.html

Hrm does this actualy work?

 

[Bert H]

Does it work?...I would have some doubts...

As far as the 'substrate being depleted', and 'fertilizing the water column causes algae', well I thoroughly disagree with the latter, and don't worry about the former. I've been fertilizing water column for a while with no algae blooms, as have countless others around here. Do a search for some of Tom Barr's posts on his 'Estimative Index', and about fertilization. It's a lot cheaper, and it works.