Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
The cheap junk from Harbor Freight will let you test the flow rate of different sized pumps, then get a quality one, perhaps Becket or Little Giant.
I have used both, and had very good service from the Becket product line.
For smaller tanks (under 20 gallons) about 100 gph pump is enough.
For larger tanks something around 300 gph is better.
When refilling I set up water in a rubbermaid garbage can with whatever that tank needs (peat, coral sand, dechlor...) and pump it in holding the tubing horizontally so it does not disturb the substrate. Smaller tanks need the smaller pump, even when pumping it up from the bottom of the barrel.
My property is sloped. There is one garden that will drain really fast (lowest point) and two areas that are sort of so-so. The rest of the garden (over half the property) is better reached by pumping, water won't maintain a siphon. There is some drop, but it is too shallow to work.
Often I will use a gravel vac to siphon, but just dump the water into a container on the floor next to the tank. Use that water to clean filter media. Then pump that out via sump pump and garden hose. That goes really fast! I use a plastic storage container that holds around 15 gallons to do this.