Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
I do not think a slight overdose is too much, perhaps up to double.
If you know you have overdosed one day, perhaps skip the next dose.
If you massively overdose, then I would do a giant water change right away, and add a chelator. It will say 'locks up heavy metals'.
If you have a high CEC substrate that will probably lock up a lot of the minerals for you. Then the minerals will be available to the plants without being in the water column.