Not enough nutrients for plant mass
One of the biggest mistakes you can make in a planted tank is to reduce fertilisation in an attempt to get rid of algae. In fact, this will lead to more algae, as the plants stop growing from a lack of all the necessary nutrients – allowing the algae to use what’s there instead. You can’t starve algae without starving plants!
Plants need more nutrients than algae to grow lush and healthy. Algae can thrive from a very small amount of nutrients, whereas plants really need a balanced mix of both macro and micro nutrients to survive.
Achieving the right balance can be difficult. Regular dosing with a comprehensive fertiliser is essential. You need to consider the volume of water in your aquarium, plant mass and just how “hungry” your plants are.
For example, in a low-tech system using medium to low lighting and no pressurised CO2, plant demands will not be very high. Fertilisation will still be required but at a reduced rate. Fertilisers such as LCA Low Tech Complete and LCA NP Free are ideal for these systems as they supply a smaller amount of nutrients.
In a tank using intense lighting and pressurised CO2, your plants will want to grow more vigorously and will rapidly use up the nutrients you supply. Estimative Index (EI) dosing with fertilisers such as LCA All In One Premium is an excellent way to ensure you’re delivering enough nutrients – in fact, dosing with the EI method ensures an excess of nutrients are supplied, so you can then focus on lighting and CO2 if there are any issues.
You can also add root tabs to your substrate to enrich it or to target specific nutrient-hungry plants.
To reiterate – you need to find the right balance of nutrients for your tank – not too much, not too little.