Planted Tank Guru
Join Date: Nov 2009
Location: Missouri united states
Seachem equilibrium is mostly calcium,magnesium,and will harden your already hard water further.
Better trace mineral source would be CSM+B or Seachem's Flourish comprehensive.
If nitrate reading is from tap,,you might not need much KNO3.
I run low tech 80 gal with weekly water change, and after each water change ,I add..3/4 tsp KNO3,3/4 tsp KH2PO4,and next day..1/2 tsp CSM+B.
Plant's respond well and no algae to speak of save a little BBA on some wood which I can live with.
I don't need pottasium due to it's presence in KNO3,KH2PO4. but tank's of mine are all low tech.
Once you start adding higher lighting, CO2 or supplement's (Excel,glut,etc,),you are no longer in low tech method and may need more nutrient's and likely better ,more stable,CO2 distribution.
For your size tank,,It will be expensive to use supplement's like excel,glut,which need to be used each day or close to it to be very effective and to create stable source for plant's.
I would stick with low tech,or go all in for CO2 injection.