Aquariums: What the heck is this? Eggs??

I don’t know what this is or who is making it, but this gunk always reappears like a week or two after I remove it. See below for inhabitants:

• two Bristol shubunkin goldfish
• One panda corydora
• Three rosy barbs
• Six cherry barbs
• Four neon tetras
• One golden dojo loach
• Ramshorn and nerite snails