here is what i would suggest. if u really like this tank,print the picture out and take it with you when you go to the store unless u plan to buy online. study that plant layout and what the plants look like.
the tall grass plant in the left side up front you could use your Hairgrass. foreground i would say try some four leaf clover. it grows slower but in time if u have patience(nothing i have) it will create a nice ground cover. the plant on the left is a rotala so maybe try some Rotala sp. 'Colorata'
. it gives a nice green yellow color and grows in fast for me so u should have that side grown in in no time.
if you want some feel free to PM me and i can get some lined up for you as i need to do a trim.
the plant on the left i would go with something maybe on the size of
again i can get you some of this.
keep with the smaller form of java fern if u want it in the middle. u could also try ECHINODORUS PARVIFLORUS 'TROPICA'
this should be an easy and easy growing setup oh wait i forgot the red plant
i can have a few trimmings for you in about a week of ROTALA WALLICHII
this is by far one of my favorite plants i have!!!
good luck and let me know if u need the plants