Good luck, I use a siphon on my sand in my ten gallon, and the siphon sucks out a little bit of the sand everytime. Its not that noticible in my 10g but I think it might be in you 2.5. However when the sand does go through to the bucket it settles on the bottom. So when you put water back in I guess you can put the sand back too, it might trap more waist but its better than nothing. Or you could rinse the sand everytime, but that would suck.