Sounds like eggs to me. I've never heard of a white algae.
Your tank, I think this has been mentioned before, is much too small for a shoal of tin foil barbs. They reach adult size of 35cm or 14" and require a huge aquarium to thrive. Keeping them in a 29 gallon aquarium will stunt their growth and cause premature death.
If you have no snails, I am at a loss of what they could be. Snails will lay eggs where there is a food source for their young, and on the glass where it gets the most sunlight would be ideal for them.
Breeding tin foil barbs has not been documented except in large public aquariums having thousands of gallons. Rosy barbs breed readily in tank, but they are egg scatterers. You would not see eggs stuck to the glass of an aquarium.