Chain tensioner (or tug) for single speed QR dirt jump bike? Recently i have started to learn no foots on dirt jumps, but i have noticed my cranks can sometimes spin in the air leading to some dodgey situations.

I believe having more tight chain would solve or help solve my issue of ghost peddling. But as i have a QR rear (with horizontal sliding dropouts) i am unable to get it tense enough by hand. Is there a way i could get some sort of (BMX style) chain tensioner?

Cheers.
Wrong approach.

On a single speed bike the chain needs to be tensioned properly. If you tension the chain too much - either by sliding the rear wheel back too far or apply too much force with and external tensioner -  you will massively accelerate wear on the chain and sprockets and make it much more likely that you will break the chain.