Any kind of manure is good for plants.

Probably the stuff in the pond would be better than "bagged stuff." which is usually just compost that will turn to muck. Sandy loam is great, and maybe you have a layer of that in the pond bottom; or it may be be less sandy than your garden soil because sand doesn't wash around as much as clay and silt. If it is heavy soil, I wouldn't use a lot of it in a potting mixture. If it is sandy loam, you could use it in pots mixed 50-50 with something like Miracle Gro orchid soil.

You can check the texture of the pond soil yourself. Search on--soil jar test. It would be good to get a soil test through your county extension agent.