Rookie mistake

[Juno]

I’m getting back into the hobbit after being out for years. I made the mistake of setting up a used 34 gal nano yesterday with the old sand that came with it. It was from an established system that was broken down a few weeks ago. My thought was that the bacteria would help me cycle faster, esp since all the rock is new/dry. Now I’m thinking I’ve just ruined my water with excess waste and set myself up for water quality issues. I’m willing to take this slow, start over, do it right. Should I vacuum it all out and start over?

 

[Reefing Madness]

I'd drain that thing out, rinse the sand really well, and start over.

 

[Gustav22]

I'd drain that thing out, rinse the sand really well, and start over.

Seconded, once the sand is rinsed really well it’ll let your own bacteria community establish itself in your tank. It’s too early in your tanks life to not start fresh I would think

 

[Juno]

I agree. I’ll work on that tomorrow.

 

[Mr Fishface]

Let us know how it goes! I bet you'll see a good improvement in the water.

 

[rkpetersen]

Agree with restarting with fresh sand.

Also -

 

[Juno]

I did rinse it a little. It looks fantastic. It’s clear and pretty. I was going to wait a few weeks to test it. Maybe I’ll go ahead and test it to see if it’s got crazy phosphates or nitrates? If not, could it maybe be ok?

 

[rkpetersen]

I did rinse it a little. It looks fantastic. It’s clear and pretty. I was going to wait a few weeks to test it. Maybe I’ll go ahead and test it to see if it’s got crazy phosphates or nitrates? If not, could it maybe be ok?

That's not unreasonable.
Check your water now; at the very least, you'll have a baseline to compare future measurements against.
Keep in mind that sand can continue to leach phosphate for some time.