Hello and welcome to FF Tim. Don't see anything there that could hurt frog; although if filter freaks out the frog anything could happen while you are not looking. Wow, 21 years is a long time, congrats !

Red injuries can represent an infection. Recommend treat with Melafix (fish natural antibacterial) mixed according to bottle label directions for 7 days or until frog extremities are healed.

ACF can get stressed by strong currents and noises. Raising water level can help reduce filter waterfall effect. Just make sure tank is covered so frog does not get out.

Gravel is an impaction hazard; guess your frog knows better than to eat it after 20 years in similar set-ups. Good luck !