I have about 0 I could spend on the project, I live in a rural area so I have access to all sorts of feed tanks and stuff – does anyone have any ideas? Any info?

My dog is a medium/large size so the tank will need to be a minimum of 3 feet deep. Plus, with winter coming I need something I can set up and work in my basement, so it needs to be somewhat leak free and small enough to get down the basement steps I guess. Any ideas or help would be great!

I have access to tools and I’m somewhat competent using them, and I have a friend who’s an electrician and might help if anything electrical is needed.

Mostly I want the tank to be safe! Second I want it to be a good work out for my dog.
My dog is under vet supervision, he’s on a weight loss diet (he literally eats 1 cup of quality dry dog food and he weighs 70lbs, he’s about 15-20lbs overweight), the issue is that he isn’t loosing weight, it’s been over a year and because of his arthrits he can’t really be walked, so I want to try hydrotherapy. He needs to loose the wieght because it will make him feel much *much* better, the vet agrees. I’ve called every vet clinic and groomer and asked within 65miles of where I live and none know of a place that offers hydrotherapy near here – if I were capable I would drive 150 miles and take him weekly, but that would cost wayyy too much, which is why building a hydrotherapy tank is my best(only) option!
What I’m thinking of/need help with is a way to generate a current that my dog will have to swim against in a safe, effective way .