That's a very good question! It seems some people can get away with that style of dosing; others can't. I am in the same camp in that I've always got high nitrates. I've always just dosed EI levels anyway. I'm starting to experiment with lowering my KNO3 dosing. Too early for results. You could either try low KNO3 dosing and then watch your plants to see if they get upset, or just keep KNO3 dosing to regular levels because word on the street is that 80-100ppm+ is possibly where it can start to hurt fish, if that.
The nitrogen can get a bit tricky in a planted tank. Yes, the "common wisdom" is that N is not harmfull to plants / fish in relatively high concentrations but I have 2 issues with EI's methodology:
- if your tank has naturally high levels of NO3, adding more of it and then removing it with water changes seems wastefull, just like moving dirt around
- EI approach is based on having "unlimiting" plant food and doing weekly water changes that "re-set" the tank and that eliminates / minimizes the need for frequent water testing. My problem with that approach is that nitrogen can build up because it comes from multiple sources:
* from fertilizers (KNO3)
* potentially, from your tap water
* fish food
* fish waste (ammonium to NO3)
* organic decay (plants, algae, driftwood, etc.)
For my tanks that hoover around 20-40 ppm of NO3 from week to week without KNO3 fertilization, I stop fertilizing KNO3. I do test for NO3 once in a while, and if that tank's KNO3 starts to drop towards 10 ppm I re-evaluate that tank's management.
The obove does not help the OP as he will not be able to actively manage the tank. But my assumption would be that his NO3 levels will be rising in his absence: dirt substrate in a new tank, transplanted plants, less frequent maintenance of water / plants / organics, and the common fish over-feeding.
In his situation, I would not completely eliminate KNO3 from his fertilizer BUT cut it down substantially to, say, 1/4 of the recommended ammount.