I usually try to stay away from that kind of product to cut on the cost but I wanted to give it a try in my little non-co2 30 gallon tank. BTW Excell does not raise the CO2 level, it does increase the availability of Carbon.
The product worked well! Within 30 minutes of treating the tank, all my plants were pearling. After a week, already my plants are greener, and new growth is visible.
According to Tom Barr from the Barr Report, Excel will not add enough carbon to the plant’s needs to drive high light tanks. It takes longer for the plants to use it than CO2.
What about algae?
According to many, Flourish Excel can be use to kill algae but Seachem are not willing to state this as such. They do acknowledge that it does have an effect on it though.
While some aquarists intentionally overdose this product to kill algae, some others say that overdose from day one may kill the fish. If you build it up slowly then you shouldn’t have any problems.