You cannot beat an oxygen system. Aerators can infuse only a tiny fraction of the much needed oxygen, simply because it uses atmospheric gas which is only about 1/5 oxygen.
Water has a finite ability to absorb gas... once it is saturated, that's it... no mas! No mas good gas or bad gas.
The cash outlay can run between $200 and $450 depending how large and elaborate a system you purchase. If you understand welding gas, regulators and diffusers and have cheap access to proper components you might get it done for about $100. Be advised though that an improperly designed system can be dangerous.
Easiest and simplest I've seen is the FishFlO2. It uses Bernzo-matic disposable oxygen cylinders and comes with built in regulator, hose, and a good diffuser. Price is around $200 and it will outperform any bubbler or aerator you care to compare it to. A cylinder of oxygen retails for about $10 and will get you through several days of operation.