Tried building a pond from old pallets. Big mistake.
Got this idea from a Pinterest board. Thought I'd make a cheap backyard pond using free pallets. $40 later with liner and nails, I filled it up. Water poured out faster than my hose could keep up. Learned pallet wood warps and splits when wet. Should have just bought a preformed tub. Anyone else try a cheap pond build that failed?
Start with the lumber you already had on hand. That tarp was probably the bigger problem than the wood. Tarps aren't made to hold water under pressure. Even a cheap pond liner from a hardware store would've worked better. The wood swelling and nails popping is just what happens when you use construction lumber near water. You basically built a sponge cage and filled it with water.
Tried the same thing last summer with scrap lumber from a shed demo. Lined it with some cheap tarp I had laying around. Water was gone in 20 minutes, just a muddy mess with a few stranded minnows. The wood swelled up so bad the nails popped out and the whole thing collapsed sideways. Ended up with a pile of wet, twisted boards and a muddy hole in the backyard.
Did you at least get a good story out of it before the whole thing turned into modern art? I built a little pond once and used those cheap pre-made liner kits from the home center, learned real quick that paying for the thicker stuff is cheaper than buying it twice. The minnows swimming in the mud is honestly a vibe I can relate to on a personal level.