Excel and equivalent products work, but not as effectively as CO2. They also have side effects. For one thing, those are not good to take big risks with. They are potent chemicals that when misused can give you health issues. They are also incompatible with some plants. But, they do have the added benefit of being slightly effective, at normal dosages, in killing some algae.
I use Excel off and on, and have switched from DIY CO2 to Excel for my low light 65 gallon tank a week ago. This was done because I had excessive leaks in my DIY apparatus, which I couldn't easily find or fix.
Read they can kill Vals?