CEDAR FALLS -- A whole other world exists in Mark Riehm's basement.

It's full of vibrant color, fluid movement -- and a whole lot of water. In two saltwater tanks that share a corner of Riehm's home live a myriad of fish -- clowns, emperors, tangs and even a puffer.

These days, having pet fish means so much more than plopping a plain old goldfish in a round bowl.

"It's their own little ecosystem," says Riehm, pointing out how 125 and 220 gallons is plenty of room for personalities to come out.

"The two yellow tangs hang out together, and the other yellow tang hangs out with the purple tang."

Some of Riehm's fish will pick a spot in the tank and fiercely defend it. The neon gobe is the most popular fish on the block, and the puffer puffs when he gets excited.

In all, Riehm has 28 fish. These pets may be small, but that doesn't mean they're easy to care for. Managing his tanks include being able to tell aggressive fish from the non-aggressive ones, checking nitrates and nitrites and making sure the water cycles properly. Every month or two, Riehm also has to change 25 percent of the water -- which amounts to more than 50 gallons of the larger tank.

It may sound difficult, but owning saltwater fish actually has gotten easier.

"Saltwater is becoming increasingly popular because the expense is decreasing," says Brandon Gruwell, an animal specialist at Petco.

Some fish lovers who desired their own ocean were reluctant to start saltwater aquariums in the past because the fish had to be pulled from their natural habitat. Now, says Gruwell, increased captive breeding allows for all the color and none of the guilt. And the animated hit "Finding Nemo" pushed aquarium sales through the roof.

Don Hill has kept aquariums for more than three years, and switched from freshwater to saltwater about two years ago because he desired having fish as they live in their natural habitat. Hill has two saltwater tanks at 150 and 125 gallons. One tank contains coral, which requires extra expense and effort, but gives Hill's tank the natural look he desires.

"My attraction to the hobby is the idea of keeping things alive and having them thrive and reproduce," says Hill. "I wanted to have a tank set up in a way that (the fish) can actually thrive as they would in the wild."

As a rule, saltwater fish are more expensive than freshwater fish, with fish at Petco ranging from $4 to $110. The largest aquarium for sale at Petco is 125 gallons. Gruwell says most people start in the 10 to 29 gallon range, though he recommends customers go for something at the larger end of that scale if they're enthusiastic about the hobby.

"Larger tanks are easier to maintain because they're more chemically stable. It's easier to catch if there is an inconsistency somewhere in the tank," he says.

Serious tank owners know which fish they want, and they'll request them. And some come by weekly when they know new fish are coming in.

"We get all shipments on Wednesday for our saltwater fish. It's amazing how many we get in on a regular basis," says Gruwell. "If we're getting something new or exciting, a small network of people in town, if they're interested, come in and pick it up," he says.

Jay Kirchhoff is still working on increasing the number of fish in his 75-gallon saltwater tank. He also has a freshwater tank, and though the freshwater fish are easier to care for, he gets more joy out of his three brilliantly colored saltwater fish -- a red and black flame angel, a yellow tang and a purple tang.

"(Aquariums) are so unique and so vibrant," says Kirchhoff. "When they're done up right, they look like a picture that moves."

Contact Kelsey Holm at (319) 291-1464 or kelsey.holm@wcfcourier.com.

{M3Here are some of the most popular fish found in saltwater aquariums, according to aquariumfish.net

{M3Angelfish:{M3 The most popular of all saltwater fish. Darts around rocks.

{M3Anthias:{M3 Among the most colorful fish. Often seen in large schools near ocean shelves.

{M3Basslets:{M3 Colorful hardy peaceful fish. Need hiding places in the aquarium.

{M3Blennies:{M3 Common to tide pools and reefs. Elongated bodies. Typically bottom dwellers.

{M3Boxfish: {M3Slow shy fish with box-like body and beautiful color patterns.

{M3African Flameback Angelfish:{M3 Feisty, will often spawn in the home aquarium. Males and females can be kept together if introduced simultaneously.

{M3Butterflies:{M3 Characterized by square colorful body with lower protruding beak.

{M3Cardinals: {M3Named after common red color. Considered easy to keep.

{M3Clownfish:{M3 Perhaps the best known of all fish ("Nemo"). Hide in poisonous anemones.

{M3Damselfish: {M3Very hardy and playful fish. Most colorful when young.

{M3Dottybacks: {M3Brightly colored popular fish, swim in and out of reef rocks.

{M3Dragonets: {M3Among the most colorful and uniquely patterned fish. Challenge to keep.

{M3Eels: {M3Often aggressive. Some species have distinctive patterns.

{M3Gobies:{M3 Peaceful hardy fish with interesting behaviors. Largest family of fish.

{M3Groupers:{M3 Renowned for comic personality. Can grow very large.

{M3Hawkfish: {M3Hardy, colorful. Perch on rocks and coral searching for prey.

{M3Pajama Cardinalfish:{M3 Very hardy, will spawn in captivity.

{M3Hogfish: {M3Hardy, colorful, semi-aggressive. Gluttonous appetite.

{M3Jawfish:{M3 Curious fish that tunnel and stir sand.

{M3Lionfish: {M3Graceful, showy fish are nocturnal and notorious for their venomous spines.

{M3Pseudochromis:{M3 Brilliant colors. Often feisty. Similar to dottybacks.

{M3Puffers:{M3 Docile. Like to swim and hide. Blows up when frightened.

{M3Yellow Clown Goby: {M3This is a reef aquarium favorite and is as fun to watch as it is attractive. Will spawn in captivity.

{M3Rabbitfish: {M3Have small, rabbit-like mouths, large dark eyes. Calm temperament. Colorful with venomous fin spines.

{M3Sharks and rays: {M3Fascinating but difficult to keep. Eventually outgrow aquariums.

{M3Tangs and Surgeonfish: {M3Popular fish, compatible with others species but aggressive towards other tangs.

{M3Triggerfish:{M3 Hardy, popular fish. Can be hand fed. Make click and grunt sounds.

{M3Wrasses:{M3 Colorful, moderately aggressive. Second largest family of fish.