Features:

• Relatively cheap (about $9)
• Very good performance

Features:

• Really cheap (~$6)
• Performs enough to get the job done.
• If it breaks, just buy another one.

The performance of this pump is very good and the pump will still produce plenty of bubbles when the air stone is fully submerged in a five gallon bucket filled to the top with salt water.

There are a few problems with this pump that have to be challenged.  First of all, the switch on the top of the pump is very poorly constructed and breaks at the slightest sign of corrosion.  Second, the battery compartment is not waterproof so you will have to take extra care to keep water out.  

To alleviate the problem with the switch breaking, I take out the switch and solder the two wires together inside the pump.  That means the only way to turn off the pump is to remove the batteries.  After I remove the switch, I plug up the hole where the switch was located with silicone.

This is my favorite pump due to its low cost and very good performance.  This pump has some problems but they can be fixed with some simple steps.  A last word of advice is to put your pumps in a Ziploc bag while using it.  That will extend the life of your pump big time!

This pump performs okay but not as good as some of its competitors.  When you submerge the air stone all the way to the bottom of a five gallon bucket which is full of water, the pump lags.  I can use this pump effectively since I don't fill up my buckets to the top.  They work well for me.

The only other problem besides low pressure at high water depths is corrosion.  This pump will succumb to corrosion a lot faster than other portable pumps.  Every metal piece will corrode if you don't take good care of it.

This is my cheap alternative to buying a portable pump.  When I need a pump now and don't have the time to go to your local fishing store, stop by Sports Authority or Wal-Mart and pick up this affordable solution.