I was planning on getting a 29 gallon tank and was wondering what fish would be good tank mates for a rainbow shark?

Rainbow sharks are aggressive, the minimum suggested tank size is 55 gallons. If you insist to get this fish, do not get anyother bottom dwellers, because they will be harrassed all the time.

You will want mid-top dweller fish that can stick up for themselfs. A species of rainbow fish that does not get too big,could work. like Madagascar, austrailian or turquoise rainbows. Lamp eye tetra , cherry, odessa or gold barbs. you could gett a single gourami.

Ohh - you could do a tiger barb tank, just tiger

barbs and the shark, you could mix albino, green, or glofish tiger barbs with regula ones, and keep 8-10 in that tank

Though i still would not recomend a rainbow shark

Loaches, small schooling fish and snails would be your best bet. Careful not to overstock the tank.