Typically vinyl tarps are water resistant not waterproof. Your best bet would be to test the tarp. Make a bag by bringing the 4 corners together and hanging it if you can. Then fill it with water and see if it drips after a while. If it does, I would recomend using an actual waterproof pond liner. You could also use the tarp as a base and cover it with a lighter gauge pond liner.
Making a pond is a pretty big commitment in money and time. I would go with something proven, like a pond liner.
When I was a kid, we had pet ducks. Dad built a swimming area for them with a tarp. Over time, the UV rays of the sun would break it down.
The tarp needed replacing fairly ofern.
when we made our pond we used a liner in the hole and then placed our stone over it with concrete in between for the extra protection and to keep the rocks in place
I have used clear plastic sheeting 4+ ml also called AG Film as a pond liner in the past. I turned my sand box in to a pond. If you want to try the idea for a year or two it is a cheap option. Any Tractor Supply will have the stuff. http://www.tractorsupply.com/en/store/ag-film-45-ml-24-ft-x-100-ft
Which one would you enjoy looking at more? A cichlid's profile side view or from the top down? Just watch this video around 3:00 min mark and let me know if ponds do African cichlids any justice
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I remember going to the zoo and they had display ponds where you could see into the side of the pond because one side was a sheet of glass like a plywood aquarium. I wanted to make a pond like that but never had the money for the glass and do not think it would work in ohio.