Amazon Swordplant problem

[tanker]

I have 10-12 swords in my two 100gals. From my experience, swords get most of their nutrients from their roots. Do you add any root tabs?
Despite what everyone says, swords do like lots of light. Strong light, not long light time. They can give in lower light, but with strong light, root food, they will really grow.

 

[the loach]

Even in a tropical climate like Florida you can have a tank or pond without algae.
Algae are simple organisms, pioneer plants. The formulae for algae is simple:
light+some nutrients= algae. Higher plants (aquatic plants) require more precise conditions to thrive. Once you provide the right conditions, aquatic plants will outcompete algae.
So the first question is, what kind of algae are we talking about? This is very important.

If the test is correct, and the water contains 0 nitrate, the algae are using phosphate. Get a phosphate testing kit and test the tank water and the source of the water for phosphates.
High phosphate levels will lead to excessive algae growth, and you need a balance between nitrate and phosphate. Nitrate can be added as KNO3.

Also calculate the available CO2. Once you have all the data, you can adjust NO3, PO4, pH, KH, CO2 to the butter zone where aquatic plants will thrive.