How often to add root tabs

[Kimlafeiet]

Hi all,
I have a 55g tank that I am planting, slowly but surely. So far, I have 2 swords and a windelov java fern. They have been in the tank for 3 weeks. I added 2 large narrow leaf swords, and a compacta sword yesterday.
I have tahitian moon sand, and have added seachem flourish root tabs under each sword when I planted them. I dose with API Leaf Zone weekly, and API Co2 Booster twice a week. Plants are doing well, I have seen a lot of growth from the two swords, and the java fern is staring to sprout a couple new leaves.
My question is, how often should I add new root tabs? The first two swords were planted and tabbed 3 weeks ago, and are doing great. How long do these root tabs usually last?

 

[TOMatt]

I add root tabs every two or three weeks, using one tab for each 6" diameter of growth. I should probably do it more often, but this works. My tank is almost the same size as yours (50g).

For a week or so after tabbing, they're a vibrant green. Then they start to fade a little. Then i add more. My guess would be that they last around a week, for mine anyway.

Even doing it so rarely, my wisteria and amazon swords are growing pretty fast. Every week or two i'm having to clip them.