I have seen this done , have a good volume 12v pump around 24 lpm .the pump goes near the water ,hose to intake must have a filter to protect the pump , mount fliter 30cm under piece of foam (may have to weigh filter down ) hose than to inlet (length will vary depending how close to the water you can get with the pump ) pump outlet hose than to tank . note large volume pump this is so it will push water up hill if required