Ok, so I'm brand new at this, so sorry if this question is dumb. I'm starting a 20 gal community tank that I hope to keep a betta in, but I know I need a back up plan if it doesn't work out. I don't have space for a larger (even like a 5 g) tank. But my back up plan is a 2.5 g on the kitchen table. So my question is how do you do a partial water change in a 2.5 g? I don't know if my gravel vac is small enough to work. But if I did full changes, my tank wouldn't be cycled. Can a gravel vac work in that small of a tank?