Hi Ivan,
In my honest opinion drawing a correlation between algae and nitrates is really not the preferred path. Firstly, that 80ppm reading of your test kit is not at all reliable so you might actually wind up underdosing and have more problems if you change your strategy to account for the readings. I appreciate that each person has their opinion so I'll understand completely if you disagree based on what you are observing in your own tank. The conventional thinking is that nitrates or any nutrients do not
cause algae. Following this convention, the appearance of algae is actually an indication that you may not dosing enough of something, whether that be nitrate, phosphate or CO2, or that the distribution of these nutrients within the tank is inefficient.
Nitrates and phosphates get an unfair share of the blame for algae inducement. Frequent water changes will help a lot - not because you will be ridding the tank of nitrates but because you will be ridding the tank of
NH4 and algae spores.
Now having said all that, it is true that once algae is induced it will then feed on the nutrients that are present in the tank and will escalate tremendously. This causes a paradox because the normal reaction is to stop/reduce dosing, however if the algae is a result of nutrient deficiency then reducing the dosage only plays into the hands of the algae since the plants will suffer more giving algae more of an advantage.
It's up to you of course but my belief is that in general the only solution is a combination of the following:
a) continued physical removal of the algae that is present and infected leaves.
b) review the dosing scheme with an eye towards increasing the macros NPK.
c) review your CO2 and/or filter outlet flow, use a drop checker with 4dkh water
d) in the short short term, reduction of lighting.
e) increase water change frequency.
If you'd like to give your tank size, lighting and current dosing scheme along with the photos we might be able to offer some more specific advice.
Cheers,