Dry fertilizers are much more cheaper. Common liquid fertilizers are made from dry salts as well. There is nothing else inside of the bottle. For example nitrogen liquid fertilizer cantains just a little bit of Potassium Nitrate (KNO3) and distilled water. You are just paying for a water. Why to spend a lot of money for water. You can make your own fertilizer. Or you don’t have a water at home?
You can have pounds of it in a bag and as soon as you will need, you will just make your own solution of water and dry salt. What does it mean? Your solution will be always fresh.
Every aquarium is unique and every tank needs specific amount of a specific nutrient. You can adjust your dose. You can add a little bit less of Potassium Nitrate (KNO3) if you have too much of nitrate in water etc. It’s far more better to use dry fertilizers than all in one sulution liquid fertilizers. Your plants will be grateful.