Algae problem

First, what do you mean by 'you clean the whole tank monthly'? Tear down? If so--you'll need to stop. Tanks do not need to be torn down unless you're moving it. Regular maintenance--cleaning the filter media, vaccuming the gravel, water changes, cleaning off the glass, yes, but more than monthly--I do water changes every week, more often if I have time, and will clean filters etc more often as well. If you are teating the tank down monthly, you are killing the bacteria that process nitrogen wastes. This provides more food for the algae--opposite of what you want.

Do you have test kits? If so, what are your ammonia.nitrite and nitrate readings?

Second--that is a HUGE bio load. Those fish will be way too big for a 30 gallon tank--and will be stunted if kept in there too long. Silver dollars got 9-10 inches, balas get to over a foot and tend to need to be in a group, the clown will eventually outgrow the tank but is okay for now, the molly is okay, and the catfish may be--depends on their species. I would find new homes for the bala and silver dollers--they really won't work out in the long run, and will contribute to problems you have.

Do not add more fish for now! Algae eaters--some will be okay, but others will not. They tend not to eat algae their entire life, and most are picky about what type of algae they eat.

Last question first--yes, a test kit of your own is invaluable. It allows you to monitor water conditions, and verify that your water is in good shape. Testing for ammonia and nitrites is valuable for cycling and emergencies, while nitrates are a good indicator of when to do water changes in unplanted tanks.

For maintenance: I clean the substrate weekly. The filter media gets rinse clean of solid waste once a week at least, sometimes more often. During weekly water changes, I prune my plants, as well. The glass gets cleaned whenit needs it--maybe once a month. The outside of the glass is wiped free of water as often as it needs it. For the filter, I siphon solid waste out of the container, and break down the pump about once every three months for cleaning. The glass top gets cleaning about once every 6 months, or if it starts to get nasty.

I never, ever, remove my rocks for bleaching. The little bit of algae on them is attractive, IMO, and certainly does not hurt the tank in anyway. Bleaching the rocks will kill off all of the beneficial bacteria on them, reducing your biological filtration.

I don't run carbon--it's not needed, unless you are removing medications following treatment or removing tannins.

A Simple Guide to Keeping Freshwater Fish by David Burchowitz is an exellent guide--it covers all aspects of keeping a tank, and some guidance for selecting fish.

There are many references for fish sizes. FishBase.org is fairly reliable for wild sizes--and IMM, this should be the standard you strive for in the aquarium as well. Otherwise--there are several good books that will help out. Baensch is the best, but costly. I would not trust PetCo--while there are a few people that are experienced and knowledgable, they are few and far between. Most are familiar with the myths, but not the facts. I'm willing to bet that most of them will tell you that it doesn't matter that balas can get to 12 inches and more--'Fish only get to the size of thier aquarium'. This is hogwash!

If the employees are telling you to set loose an aquarium fish, I don't think I would ask them for any more advice. It is highly illegal and risky.

If they're also saying three 6" fish aren't too big for a 29 gallon, I would suggest not to go there either.

Yep, I really don't use carbon as a regular part of my filtration. I have it, so I can use it if needed, but the majority of the wastes in your tank are biologically removed, or diluted with water changes.

Good call on not releasing fish--big time no-no.

Sorry on the mis-spelling--too many syllables ; The Simple guide series are fairly recently released, but I picked mine up at Barnes & Nobles.