So if I get the root tabs in and do away with the fertiliser this will help reduce algae?
Doing that COULD reduce the algae.
How long do you leave the tank lights on for during the day?
Does any sunlight go into the tank?
How much foods do you add into the tank per day?
How often and how much water changes do you do daily or per week?
I ask all these questions because there is no one single answer that could help you, there are usually several factors that makes algae appear in tanks.
Usually it’s down to lighting hours, 7-8 hours is the average times, any more light could increase the chances of problem algae.
Poor water quality could be factor in algae, too much foods into the tank could contribute to poor water quality.
Not enough water changes and tank maintenance can also add to the poor water quality. Most of us do at least 50% though would say it likely to be nearer to 70% of water changes once a week and cleaning tank glass of algae and syphoning up dead leaves, leftover foods and debris help keep water quality at a optimum level.
Direct sunlight into tanks can be a particular problem as this vastly increases the chance of algae appearing, particularly green algae.
So if you can reduce the sunlight going into the tank, this would help greatly, either by closing curtains/blinds or moving the tank to a more shaded area will be of great benefit.
The addition of ferts, be it root tabs or liquid ferts or both can contribute to algae, especially if you overdose the recommended amounts.
Algae, needs exactly the same as live plants in order to thrive, and if you have very few live plants then algae will take the lions share of these and thrive then problem algae will be in abundance, but if you have quite a few plants then the plants will take the lions share of the nutrients and such then the algae will simply starve and hopefully die off.
But if you follow all the above advice then algae should be well under control.