I'm posting some information about a well balanced line of basic fertilizers available in Europe (maybe also somewhere in US), all of the products are made in Poland. I'm using these products in my tanks for more than 4 years and the results are very good.
I hope I won't violate any forum rules by this post.
Aqua Art Classic:
Contains: iron, manganese, zinc, copper, molybdenum, boron, potassium, magnesium in easily digestible form.[censored]Adaptations in aquariums where tap water or mixed water with reverse osmosis (R / O) water is used for the variation.[censored]
Dose directly into the aquarium after partial water change 1 ml per 4 liters of water.
Aqua Art K+:
The potassium contained in K plus is one of the basic nutrients for plants.[censored]The K plus makes the nitrogen and phosphorus in the aquarium water, from the metabolism, easy to digest for the plants.
3 ml per 10 liters of water.[censored]To enhance the care effect, K plus can be given daily at about 1 ml per 40 liters of aquarium water.[censored]
Aqua Art Carbo:
Planta Gainer Carbo is an easily digestible and efficient carbon fertilizer.
Aquarium with an average plant of 1 ml (one press of the dispenser) for every 50 liters of water in the aquarium per day.[censored]
Aquarium with lots of plants 1 ml per 25 liters of water per day.
Aqua Art Macro Green:
Macro-nutrient fertilizer specially formulated for slow growing plant species such as Microsorium, Bolbitis, Anubias and others that do not require too much light.
Dosage daily, selecting the dose for the individual needs of the tank - eg 1ml for every 40 liters of aquarium capacity.[censored]