I use a home made undergravel filter for my twenty gallon tank. I can't say if it is the most efficient way to go but it provides a very effective medium for Nitrogen processing bacteria.

I used PVC plumbing and egg crate louvre available from the electrical department at Home Depot and some plastic screening on top of the louvre .. less then $25.00. Ofcource you will need to add an air pump and some air stones for inside the tubes.

A mechanical power filter may also be an useful addition.

Good Day ...

I would never reccomend a UGF to any one over a 2 gal tank. A Whisper or Aqua Clear or Regent/Marineland Are all inexpensive HOB style and for a 15gal should only be about $10-$15. You can rinse the ffilter cartridges instead of replaceing them. I just replaced mine(Regent from Walmart after a year)If you insist on a UGF then you should break down the tank every 6 months and scrub the plates.For a 15 gal dont get a Pleco if thats what you had in mind(they get huge to 20") get oto cats very smal, about 3 thay do a great job and dont add much to the fish load.

Does anyone have any better ideas/advice? Such as are live plants better for an aquarium but cause more of a mess? Let me know please!

Well I dont mean to be a hassle. But I was hoping to know what plants are easy to maintain in a fish tank, and what fish, preferably neat looking ones will hold up well. I have had fish tanks but I want to try this one right.

Octoganl tanks are usualy hard to light because of their depth and small surface area. Try to getat least 30Watts flourescent, 6500K 40watts may be better cause of depth factor. Any red or purple plants need at least 3.5-4 watts per gallon. If you have an incadescent fixture exchange the bulbs for the compact florescent spiral type. Walmart has 2-packs 15-35 watt per bulb for about $8. They are marked "Daylight",and are made by "Lights of America". On the package and base of the bulb itself it says 6500K. Soft White, Cool White are no good as they are to yellow and green. Plants need mostly Red and Blue so the daylight bulbs are full spectrum. Java ferns and java moss are very good lowlight "beginner" plants. Use "Florite" by seachem as your gravel/substrate. Use "Flourish Excel" along with "Flourish Comprehensive Plant Supplement" for fertilizer. I prefer planted aquariums for there natural ability to "nitrify" the water but mostly because of the beauty and compliment to your fish.If you want live plants then a UGF is out of the question. As far as efficiency if you go planted start the tank with tap water and plants from the begining. When the plants start to thrive stock fish slowly. Do a 35% water change every week, nice thing is gravel vacuum not necessary, just hover to clean the fish crap. Every 6 months pull the plants and thorough gravel vac. Non-live plant tank, find a freind who has an established tank. Plead with him to give you his filter media or let your filter run in his tank for 2 weeks.Then add a free and clear type cleaning ammonia. This is call a "Fishless Cycle" search it on the web for a better detailed description. As far as filtration the "Whisper" is a fine model. About $10-15 and easy to maintain. They just changed design and I bought one for a 10 gal QT tank. It is very quick and simple to use. Best advise is take time and do it right. If you slap it together and hope for the best it will bite you in the arse. Also a 20L tank is better for planted and about $25 the other equiptment is the same as you would use for the 15 gal. You can always use the 15 for a QT tank. Some will argue that a small tank like the 15 planted with no mechanical filtration is OK. My opinion is different.

live plants help keep the tank cleaner. you can get plant bulbs or live plants at your local petstore. and when the tank is ready to clean, just rinse the plant with water.