Hi all... haven't posted for a while here, but just wanted to make a comment about oxygenating the water.
The bubbles from an airstone do not actually oxygenate the water. Oxygen transfer only happens at the surface, so you actually need your water to circulate so that water below the surface reaches the top to pick up oxygen.
What bubbles from an airstone do is sort of push a tiny column of water up to the surface with each bubble. So, it helps the water become oxygenated this way.... sort of circulating it, but the bubbles it makes don't actually add oxygen to the water.
Circulation is the key. :)
And good luck with your orandas! I've got 6 goldfish, one is a blue oranda named Mr. Slate ..... he's the baby of the bunch right now, but will outgrow them all!
Julie (I need to redo my siggy line..... so plain signature for now)