Does ds need fluid other than bm now started in solids?

[Rubykippers]

Started ds 5 1/2 mo on baby rice two days ago. He is still having bm on demand just not sure if extra fluid is needed.

He probably doesn't actually need any extra fluids. The BM still gives him plenty.
Also, the first solids will be exciting enough without adding any other new experiences.

However, it would be quite natural to start introducing extra fluids in the not too distant future.
When giving meals you can make a drink of water available so that he can start to learn about drinking something other than BM from a container other than Mummy.
He won't drink much (if any at all) in the beginning, but it's a good idea to have something on hand for those occasions when the food is a little hot or something needs washing down in a hurry.