What Does Ei Mean?

[sadielmorris]

I've been reading through these posts and one thing keeps coming up. Some people seem to be using the EI method and have great looking tanks. What does EI mean? I can't seem to figure it out, it's driving me crazy.

 

[nry]

Estimative Index - see the pinned thread

 

[The-Wolf]

EI = Estimative Index
The Estimative index is a simple method to dose nutrients for any tank without test kits

I'll let the plant experts elaborate on that a bit more