I have a variety of indoor plants that seemed to be quite happy when I finished the first bottle of this stuff so I got them another.
It doesn't mention that the top is a dropper which makes it easy to measure out a dose. I use it once a week during the growing season and it last around a year.
The only downside is that after a while the bottle develops a powdery residue on the thread (I assume from the odd drop that lands there). When the bottle is opened this tends to drop off so make sure you don't open it over a white carpet.
If you want to save a few pence search Amazon because I got several hits for this at different prices.