You stick to the EI dosing regime:
It is made so that you don't have to use test kits unless there's something going wrong in your tank. The objective of EI dosing is to supply your plants with enough of the nutrients and micronutrients that they need in order to outcompete algae, they is suppose to be more ferts added to your tank then your plants actually need. Algae shows up in order to compete for light, not nutrients from what I've read. In EI, there's weekly water changes that is there to make sure and help prevent the case of overdosing that you fear. As long as you stick to it, then you shouldn't fear.
Think about it though, there's nutrients in the water all the time in some very nice looking tanks.
Cause of algae is due to a few reasons:
1. Insufficient amounts of nutrients. This is one thing brought up about maintaining a balanced tank. To maintain one, you must make sure no nutrients bottom out and plants have enough of each nutrients. Any lack of nutrients might trigger the start of algae. Algae spores are already in your water, they're just waiting for the right conditions to start growing.
2. Fluctuating or not enough CO2. Keep your CO2 at around 30PPM or for drop checkers, keep the color to around yellow. Also note that sometimes, lack in CO2 is not always due to your diffusion method or how much you're injecting, but also how much flow you have in the tank. Flow helps carry nutrients and CO2 enriched water to all areas of your tank, if you lack that, then there might be dead spots that can trigger algae in some parts of your tank.
3. Too much light, not enough CO2. You can lower your wattage, lower the time it is on to about 6-8 hours, find a way to hang your light a little higher over your tank, or find a way to inject more CO2. The more light you have, the more CO2 you'll need, the more it'll take to keep your tank balanced (review #1 if u have to).