How much fertilizer is needed for 4ft tank

[zhuzhu]

Can anyone advise how much fertilizer is needed for a 4ft tank? 2 or 3 pack?

[medicineman]

What kind of fertilizer you are referring to?
Specific brand has its own dosage recommendation. Specific bulk chemical has its own usage and dosing approximates.

You do not want to fertilize your tank with just any fertilizer (generic ones used for gardening) as they might cause a dear consequence to your tank. It is proper aquascaping fertilizer you want. 4 ft tank should be reasonably cheap enough to maintain using these.