There are three basic needs for all aquarium plants. Light, Macro Nutrients, Micro Nutrients. The more light you have the more important the other needs become.
Choosing your light is the first step in aquascaping. The more lumens per litre the more plants you will be able to successfully grow. The light is especially important when trying to carpet your tank or get bright reds or purples.
Light duration is the next thing to consider. I normally try to keep my lights on for 8 hours a day on an established tank. On newly scaped tanks this can sometimes cause massive algae outbreaks so dialing it back to 5 or 6 hours can be necessary at the beginning.
Now we need to consider the quality of the light being delivered. The color temperature is definitely something that shouldn’t be overlooked. We are wanting to use 5500k to 6500k to mimic natural conditions as best we can. The lights you see that are 7000k or even as high as 10000k put off a bluish tint and are designed for marine aquariums. So the light may be crazy expensive and bright, but it’s not the light we want.
Picking the right tank for plants is an often overlooked step. Not all tanks are created equal when it comes to plants. The taller the tank is the more powerful your light will need to be. It’s much easier to carpet an 8” tall tank than it is a 24” tall tank. Good water movement inside the tank is equally important. This can help with keeping a lot of different types of algae and bacteria from every appearing in the first place.
This is where things can be as complicated as you want them to be. I am going to try to keep things pretty simple here. There are two types of nutrients; Macro Nutrients and Micro Nutrients.
Macro nutrients are the main nutrient needed for healthy plants. They are Nitrogen (N), Phosphorous (P), and Potassium (K). The macro nutrients should probably be supplemented if you have a densely planted tank, use Co2, have a medium to high light, or are growing more advanced plants.
Micro nutrients are used in smaller amounts, but any planted aquarium can benefit from supplementing them. They are iron (Fe), magnese (Mn), chlorine (Cl), copper (Cu), boron (B), molybdenum (Mo), cobalt (Co), nickel (Ni).
Plants feed off of Co2 and use it for photosynthesis. The more light you have the more Co2 becomes necessary. If you have high light and no additional Co2 source you will most likely be promoting algae blooms. Another sign that you might need Co2 is if you have stunted growth or paling in the leaves and stems. It is important to keep your Co2 ppm over 15ppm, but under 30ppm. Anything over 30ppm can be harmful to your fish.
Iron- leaves will grow in a pale light green, yellow, or white with no spotting. Veins of leaf will remain dark compared to discolored leaves.
Calcium- New leaves will grow twisted and stunted. Tips might even wither.
Nitrogen- Older leaves will turn yellow and translucent starting at the tips. Oldest leaves may even start to fall off.
Phosphorus- Leaves will appear darker than usual and have a slight brownish look on the underside. They will then turn completely yellow and have patches of melting. Stems will grow to normal height, but will be thinner than when healthy.
Potassium- Leaves will have small pinholes mostly around the edges and tips. Sometimes the leaves may even curl inwards.
Manganese- Leaves will have yellow and white interlacing patches.
Magnesium- Older leaves will turn light green/yellow while the veins stay darker. Edges might even start to droop.