This might sound crazy but can I squeeze a sponge into the tank to add oxygen? I clean the glass of the tank with sponge every few months and I notice the amount of bubbles it puts in.
Does flourish advance have the same problems?
I'll step in and say that it's safe, or as safe as any aquatic fertilizer when used appropriately. Having said that, anything and everything in the water ends up in fish through osmosis. So modest ferts are likely 'okay', but too much (of anything) is bad.