Struggling With Hygrophila Guianensis

[lowee]

About 2 weeks ago i bought a potted Hygrophila guianensis plant. From the tropica description it says it is a fast growing plant but nearly two weeks on and it is pretty much the same size. Ive got about 22ppm CO2 and about 2.5WPG, dosing twice weekly with flourish. Anyone have any ideas why it isnt growing?

Thanks

 

[lowee]

I just have normal pea gravel with seachem root tabs in.

 

[lowee]

The tanks about 45 gallons, but the guianensis isright under a 25W tube with a reflector so its getting a fair bit of light. And the plant seems fine, except for a few small holes which most my plants do because my catfish seem to enjoy nibbling on them! So just not growing is really the only thing.