Um, Can I jump in here?
okay, here is my take on this matter.
UG filters are indeed pretty good if PROPERLY used. Using a UG filter can be a problem in an overcrowded tank and if that is the only source of filtration this can be a problem. Amonia can and will build up causing the tank to crash. If overloaded fish will live unhappy / unhealthy lives.
Keep in mind that a UG serves more than the purpose of keeping tank filtered. it also helps maintain your biological bactertia.
No!!! it is not good to totaly remove UG and clean. But, it IS very important to vacume gravel during EVERY water change. IME
This waste turns into toxic waste if left alone. Especially if left alone and stired. All that is being done is the water is being fouled by sitting waste. Which when stired up the fish are now breathing this waste. Notice how they gasp for air when the tanbk has tons of free floating muck ?
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This in itself can bring on serious problems in an aquarium.
Parasites, diseases, and in some cases ick can come about. It is in NOWAY healthy nor suggested IMO / IME that grvaerl NOT be vacumed and stirred regularly.
Now, not saying it can not be done. every hobbiest has his / her method of duing things and on how they keep there fish. but, the question remains: Is it the best and healthiest for your priced fish ?
I keep over 100 tanks and ALWAYS vacume gravel during EVERY water change. A clean healthy tank inssures that your fish will grow properly and be free of infections that may accure.
There is NO intent to start a debate here. I just want to asssure that propper advice is givin. I am in NO way an expert but have been keeping fish for a long, long, time. Over the years I have learned from mistakes. And NOT cleaning your gravel is one. Any avid hobbiest who keeps fish (multiple tanks) will tell you the same. NO not a good idea.
What I see as a problem is that many newbies take in the advivce we offer. Yes maybe sometimes it may not be the vest advice but we try. the advice taht is givin in most cases is followed through. Personaly I would really hate to hear a member asking a question on how toi medicate a tank becasue it was fouled up due to improper maint. Or not so good advice.
Again NOT in any way saying this is wrong but , I would STRONGLY have to disagree with it. I run 102 tanks some have UG filter and either a sponge and or external filter. I mainly use the UG for a good surface current. I run all my UG filters wuith power ehads which as mentioned by a membver is the best way to go.
Using a UG and a power head allows for all or most of the waste to be sucked down below the UG dilter where it sits and the bacteria feed. this is what makes a healthy tank. Good colonized bacteria and regular maint. There is a small amount of waste that is removed by using a vacume to clean the gravel. Alot of the waste stays below the filter. this is designed to help tank maint. not to be a sole part of maint.
Yes it is a good idea to completely clean every year or so BUT, it is NOT something that is a live and death sittuation. Do I suggest cleaning the UG filter, Not really. As mlong as the gravel is vacumed and kept fairly clean there is no need to worry about the tons of muck below the filtewr.
When using a power head alot of this is pushed down threw the gravel and back up the UG tubes.
this is serving a purpose. All the loose material is being pumped back up and left easy to vacume up.
Simply stirring upp the gravel is NOT enough to maint. a healthy tank and soon enough can be a real problem.
Once a day, YIKES ! I hate to see how them fish react to having muck / poop going through there gills and gill plates. Keep in mind also that fish have glands on there gills which help trap oxygen and in most fish helps with feeding. Whern the tank is stirred and all the muck is free floating the fish are inturn breathing this.
Ever done drywall work and have had to sand plaster ? That feeling of NOT being able to breath because the dust is so thick and it is irretating to the lungs, eyes, and throat. Well that is about how a fish feels when the tank is stirred up and they are forced to breath the muck.
I would STRIGLY have to disagree but, do not say it is totaly wrong. As I said to each his / her own. All we can do as hobbiest is pass on our learnign experiences and hope others don't make the same mistakes we have made along the line.
So to sum it all up,
UG filters are a good filter IF properly used and used in combination with another filter not as SOLE means of filtration. Power heads are best to use on UG.
Should the gravel be vacumed regularly with water changes ? IME / IMO YES !!!!!!!! it is a must to keep healthy, breeding, growing fish.
UG filters do have there downfalls also, most times when you vacume your tank and refill it and plug the power head back in you will notice alot of loose muck come up through the lift tubews. this is normal and is all the loose debris / waste that was not collected and loose enough that is serving NO pupose. this is what we want to vacume up. NOT stirr gravel and say, good enough even though fish look like they are in a pooop storm.
Not all UG filters are the same. some are better and alittle more high tech then others. All serve basicly the same function but some out perform others. there are many UG filters on the market and all range in price and quality.
Question : any certain reson for wanting a UG filter ?
Hope this helps,
Danny
PS. Please No hate mail.......
welcome to the forum 
?? i guess everybody has their own way of doing things, but what matters is that your fish are healthy and thriving!
