I have a tall stock tank and I use a large dog ( think golden retriever size dog) car ramp for them to access it.The problem I had with stock tanks was I couldn't find one less than 2' high. My ducks couldn't seem to grasp that they had to go up to get to the water. I built a ramp and even steps out of bricks and paving stones, but they wouldn't use them. The only way they would swim was if they could see the water and easily get in and out. Sinking the tank to near ground level is the only way they would have used it. Hopefully you can find a shorter one or maybe your ducks are smarter than mine.