Yep useing it right now on a small tank, does exactly what it says on the tin.
Basically i would only use it on medium light tanks, on tanks with high amounts of light the excel doesnt really cut it, because the uptake rate by the plants is to slow, they seem to have a problem digesting the organic carbon quick enough, whereas with CO2 they can pretty well use it up straight away.
You can also use it to supplement DIY CO2, but again i would only use it on tanks with medium amounts of light or below obviously. It does work but not as good as the "real" thing........CO2, you will get better plant growth with CO2, but for a nano it should work really well provided the light is not to high.
