Q: What kind of air pump do I need for two round undergravel filters 4" diameter for my two 1 gal. bowls?  Or would I just need to control the airflow, if so how?  Thanks =) Love my Bettas!!!I

Question submitted by Martha, Tyrone - NM

A: Ok Martha, this is going to be undergravel filter 101 :). 

Bettas are oftentimes housed in bowls because, let's admit it, bowls are convenient (and inexpensive). How to add a proper filter to a bowl is an issue that all of us betta hobbyists have to tackle at some point or another. Obviously power filters are NOT an option :). That leaves us pretty much with either a very tiny corner filter or an undergravel filter. These types of filters will need an air pump to function. The problem here is that you'll need enough air flow to run the filters, but not so much that the water movement bothers Mr. Betta. 

Back to your question. What I would do is use one pump to run both filters. That can only work if your bowls are close to each other, say, side by side or on the same shelf/table. I would pick the smallest pump you can find, like an
  Elite 799 or even smaller. Then I would get a  two way gang valve  so you can control the amount of air each filter will get. You save money this way because one pump will supply two filters. The gang valve will need to be adjusted. Here is a trick: Open valves to turn air flow up until Mr. Betta start swimming funny (showing the water movement is becoming too strong), then back it off a bit, until he seems peaceful again. This setting should be the ideal compromise between filter efficiency and betta happiness.

Remember, bettas come from stagnant water so they do not like too much disturbance, especially in small quarters. Having said that, my personal observation is that they do love water movement in larger tanks, and seem to enjoy swimming in it, for as long as they can then go somewhere in a quiet corner to take a nap :). So you must provide them with such option.

Last thing I am going to tackle briefly is undergravel filters themselves. You will need gravel for them to work. No more than 1 inch deep but no less either. You will also need to provide CONSTANT air flow. You CAN NOT EVER stop the air pump. If you do, you will cut off oxygen supply to the friendly bacteria that lives under your undergravel filters. When they run of of oxygen, your colony will die. If it dies two things will happen: 1)- Your filter will no longer be efficient (since undergravel filter are biological filter they rely 100% on the bacteria to work).  2)- The bacteria will release harmful toxins in the water, which could hurt Mr.Betta.

One more draw back: Live worms will fall to the bottom of the bowl and hide in the gravel, then work their way through the undergravel plastic tray. They cannot hurt the filter, but will eventually die down there and rot. So if you are planning to feed live worms to your betta, you will have to do so one worm at a time, and make sure your fish eats each one of them!

Besides this, undergravel filters work fine and can be a good option for a small bowl. I have used them before. Goodluck!! :)