Tropica has 2 brands of liquid fertilizer — Specialised Fertilizer and Premium Fertilizer.
The Specialized fertilizer has N+P (nitrogen and phosphates), while the Premium does not. Unfortunately, not much information is available on the exact ingredients, composition, or percentage of each type of nutrient. For example, it is unclear how much potassium the fertilizers have.
I managed to find the exact composition on the UKAPS forum:
Tropica Fertilizer Composition and Ingredients
|Nutrient (w/w%)||Premium Fertilizer||Specialised Fertilizer|
Tropica Fertilizer ppm
The composition of ingredients given by Tropica is in w/w% which is weight concentration of a solution. Usually, we want to know the concentration in ppm, or parts per million (equivalently, mg/L).
For that, we can use the Rotala Butterfly calculator. The below information is based on 1 pump (2ml) for a 5 Gallon aquarium.
Your addition of 2 ml (equivalent to 1/4 tsp + 1/8 tsp + 1/32 tsp ) Tropica Plant Growth Premium to your 5gal aquarium adds:
It is quite a “light” dose. Considering that the recommended target concentration of K is 10-30 ppm (from Tom Barr). Singapore water only has on average 1 ppm for K (potassium). Hence, the once a week dose of Tropica fertilizer Premium is definitely not enough to hit 10-30 ppm of K.