Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
For Excel, 5ml per 10G is the recommended initial dose. After that, the regular dose is 1ml per 10G, daily.
Excel is a dosage dependent toxin. As the dosage is increased, it starts killing more complex organisms. At normal dosage, it's safe to all but particular plants. At 2X overdose, it will kill some algae. At 3X, it will kill lots of algae, but starts to put sensitive critters at risk, like shrimp, and possibly cories.
If you're dosing 10ml in 40G every two days, that works out to a 2.5X overdose over time.
But Excel doesn't last long in an aquarium. Most say a day or less. Looking at it that way, you're doing a 5X overdose every two days. That puts everything at risk.
I don't even use the initial dose for this reason, and always use the regular dose (1ml per 10G daily) instead, just to be safe.
Re-read the Excel instructions carefully. I do recall another person who was dosing too much, and was also using the smallest bottle. It may be possible the instructions are shortened, and therefore incorrect, on that size bottle; and I'd be interested to know if that's the case.
I haven't used Leafzone. Seems to contain iron and potassium only. No harm in using it along with Excel, as both perform different functions. But the dosage is 5ml per 20G weekly. So you're double dosing that too, maybe more if you dose more than once a week.