Electric vacuums

[Smo4]

Has anyone tried using any of those electric vacuums selling on the internet and Amazon? I want to know if they are worth the $30-$80 pricetags. It seems like something in my tank is constantly defecating a lot everyday and I haven't even been feeding them much because I had a nitrite spike in my new tank. I've had the tank for about 3 weeks now. I just want to remove the poop some days without taking any water out. The siphon I have takes out too much water when I'm just trying to clean the gravel. Some of those vacuums I've seen will filter the water back in the tank, but still remove the poop and other stuff on the bottom.

[Smo4]

And actually I have sand not gravel.

[bill.marshall]

I use one filters the bottom sand bed, and returns water to tank, after running it through small filter .