Problem With Underground Filter

[XxTbaggerxX]

I have 2 plants in the back corners of my tank but every 20 min or so big bubbles come up from under the gravel. So now my plants wont stay down in the gravel for more than a day or two. Is the filter broke?

 

[Shelly_Otterkin]

Is your UGF ran by air or a power head? If its air pull your airstone up a bit so they are above the gravel level. Also if it is air you need to think about up grading to a power head for better water movement.
Good luck