I don’t usually buy farm-raised fish.  Too many articles I’ve read tell me that the fish are polluted with chemicals and that fish-farming pollutes the environment.  So, I dutifully check my Seafood Watch card and spend a little more on wild, sustainable, healthy fish.

When our Twin Cities blogging group, the Blog Pantry, met at Local D’Lish a few weeks ago, my eyes were instantly drawn to a fish tank set up at the back of the grocery store.  The owner, Ann, told me they were setting up a small-scale aquaponics system that would use water from the fish tank to fertilize vegetables and herbs they were planning to grow in the store.  I had seen a larger-scale version of the same thing on Will Allen‘s amazing 3-acre urban farm in the middle of downtown Milwaukee in the film “FRESH.”

Apparently, this type of closed loop, recycling system allows people to grow crops using less water while raising cleaner fish for food.  Systems like these may revolutionize the way people farm in the future.

According to an article in the Christian Science Monitor,

“Recirculating aquaculture systems, or RAS, are closed-loop production systems that continuously filter and recycle water, enabling large-scale fish farming that requires a small amount of water and releases little or no pollution.

About 99.75 percent of the water in each unit is continuously cleaned and returned to the fish tanks. Manure filtered from the water during the recycling process is used as fertilizer on nearby farm fields. The nutrient-rich water can also be used to feed vegetables and herbs in large-scale aquaponics systems, which in turn filter the water for reuse.

One of RAS’s biggest benefits is its small “water footprint,” which opens the door to commercial fish production in areas with limited water resources. (The technology is proven for both fresh- and saltwater systems.)

Cool!  Maybe someday, we’ll all have little kitchen gardens hooked up to fish tanks!

In the meantime, I look forward to a future where I can buy farm-raised fish with a clean conscience.

Here’s a fun, easy science project that I discovered a few years ago on pbskids.org/dragonflytv.  My children will do it again and again.  Even my three year-old joined in, cutting up construction paper into “fish food” and throwing it into the water.

You will need some sort of pan for water (a cake pan will work), construction paper, scissors, and dish soap.  Have your child cut out some fish shapes from the paper (around two inches long works well.)  See the photo below.  Then, have them cut a small slit in the back of the tail.  Put a few inches of water in the pan and add the fish.  Before the paper soaks up too much water, have  your child add a drop of dish soap behind the fish.  The fish should zoom across the water.  You will have to add fresh water tothe pan if you want to repeat the experiment.

The soap breaks the surface tension of the water.  Tell your child to imagine that the surface of the water is a sheet of fabric and the soap is a pair of scissors.  The soap cuts through the water, pushing the fish ahead of it.  For a more scientific explanation, have your child look up surface tension or visit the dragonfly tv website!

Don’t forget those science notebooks!  Have your children write the date, “surface tension” and record their results.  They can try using different liquids (like lemon juice) to see if they will break the surface tension.  My kids made some fish out of that foam that is used for craft projects so that they wouldn’t soak up the water!  Hopefully, the zooming fish will keep your child interested and busy for a while! Click here to see a video on how to make zooming fish.