5 years old. Still loads of little critters but plants have died.

So this ecosphere was from a pond at my parents house. I made it 5 years ago and it's never been opened. Had lots of soil from the pond along with pond weed. This year the pond weed has died off, but there are still loads of critters swimming around in there. Should I add more plants (I can get them from the same pond) or keep it as is and see what happens.

It's been a real pleasure watching it for 5 years. Really interesting.