I have a newly acquired 10 gallon fish tank with some gravel, rocks, and just recently some coral. I first filled it with tap water, a week ago, and let it filter with my hanging over the side charcoal filter, new bag, for about 3/4 of a day. I brought home some anacharis and a moss ball and planted them in my gravel. They were very green on entering the aquarium. THEN, I started researching aquariums and the plants to go inside and how to care for them. I read over and over that they need three things: nutrients, light, and CO2. I had no fish so I figured I must add nutrients. My dear mother has much love for organic outdoor gardening and so I thought to use some of her liquid fertilizers. I had not come upon the supposed ratio I recently read of 10-1-10 or 10-1-20 (?), but I figured I had supplies to get the nutrients the plants needed to them in sufficient quantities. I ended up mixing multiple bottles of brown liquids and dumping a 1/4 cup a day into the tank.
Use Dirty Aquarium Water to Fertilize Plants - Lifehacker
The biology in an aquarium is a delicate natural balance between the fish, plants and bacteria, into which water parameters also are involved. It takes a few months for a new aquarium to reach its biological equilibrium which is a balanced state for the bio load. Adding stuff like Excel is increasing the carbon by a significant amount, and this will cause that balance to become unbalanced. Planted tank aquarists who add CO2 diffusion create a different balance, with increased (more intense) light to balance, and additional fertilizer. Takashi Amano uses CO2, high light, and fertilizes several products every day because as he himself admits it is essential to maintain the balance in his type of system. At the opposite extreme is my method of absolute minimal nutrients and light, sufficient to grow the plants but not beyond that level. Regardless of which method one uses, there must be a balance or it will not be successful. My process is to start with the least and work up to reach the balance; I have taken this approach because I believe that the less the aquarist interferes (by adding this, that and something else) the more nature will maintain the natural balance.
Aquarium Plant Food & Fertilizer | That Fish Place - That Pet Place
To conclude, I would use the Plant-Gro liquid as directed (presumably once a week). Monitor the plant growth over 1-2 weeks and be prepared to adjust if needed. I need to fertilize twice a week to keep my swords lush and thriving, because my water is so soft. Each aquarium is different, with its own unique balance. And we should all know by now what can happen when we interfere with nature's balance. As with the earth's environment, so too with the environment within the aquarium.
Rapid Grow aquarium Plant Fertilizer - Select Aquatics