Crypt Roots Growing Upwards

[voo]

One of my crypts has got roots that are growing upwards, out of the sand. The others in a different tank dont appear to be doing this, so i was wondering why this one is doing so?

Here's a pic of what's happening:

 

[Sibelius]

I have exactly the same in my tank. I Don't have a clue why, but they're doing ok so I havn't done anything about it. Maybe there are more nutrients in the water than the substrate? I use liquid fertiliser, but there's nothing in my gravel substrate, so that could be it. What do you use?

 

[voo]

I dont have any nutrient substrate in this tank, just using root tabs. Can't remember if i put one under this plant so i've put one in tonight. Plant seems to be doing well otherwise, was just wondering why the roots were doing this.

 

[Sibelius]

Yep, certainly weird, but I don't think it's a problem. None of my other plants do this. I'm not at all worried about it.