Everyone with an aquarium and external air pump should spend the couple of bucks on a check valve. Most people do not realize what they are. If you have an airline running into your tank, and your power ever goes out, your airline could back flow sucking the water out of the tank. Not to mention the electrical hazard, it's a mess to clean up and if you are not home, your fish may be out of water.

Pros: Simple to use/will save you a major headache

Cons: None

If you have an air pump, you need a check valve. It's a cheap way to save your air pump if the power happens to go out. Sometimes water will back into the air hose. If you don't have this item, there is a good chance that the water will go into your air pump and ruin it. A check valve cost arount $2. It's better than buying a $20 air pump.

Pros: Saves your air pump

Cons: None

I live on a bad grid for electrical!! SO this is a must to keep water from backing into the pumps!

Pros: keeps water

Cons: none

If you own a pond, you need a check valve. It will save you money in the long run.

Pros: Absolutely needed

Cons: none

This really works great and well worth the money!

Pros: GREAT!

Cons: None