It is normal and expected to have some algae and it can even mean the system is healthy....however, since its a closed system we have to control it to a degree by manual removal and balance....
With planted tanks its a balance-you have to meet the plants needs in order for them to out compete the algae for both light and nutrients.....
Proper lights are the driving force.....what kind of lights do you have, age of bulbs, kelvin, watts and photoperiod....
Number and species of plants and how planted, type of substrate and how deep...
What kind of algae.....
For mild infestation of Ich-sometimes all you need to do is build on the fish immune response and limit stress and they will take care of it-along with manual removal of parasites with vacuum every day for 1 week....