What is your evaporation rate ATM?Yeah understand totally. You don't dose the straight liquid do you ? Only the final mixture with the RO water .... So if I started off with 0.1ml of the phos remover/RO water mixture and see how we go....... ...???
Mine is about 15 liters per week or you could say 2 liters a day, with that in mind I would feel comfortable putting a liter of RO in my tank.
With an 80 liter perhaps mix your liquid phosphate binder in say no more than a cup of RO water. What we don't want is to upset salinity levels in our tanks.
Taking this to the next level could mean that once liquid Phos binder consumption is known you might add it to the evaporation top up container.
Before I had a calcium reactor I used to dose my alk into that container.