well undergravel filters aren't too good with mechanical filteration, and you have to tear it down once a year for maintanance, cos all the detritus ends up sitting under the gravel, not actually removed from the tank.
reverse flow UG filters are better, but they also have similar problems as normal UG filters. deadspots where decorations are, and you still have to tear it down once per two years.
I prefer a good external filter and siphoning the gravel once a week
Mind you, I think UG filters have good bio filteration? I'm not sure. it also keeps the gravel itself clean of any detritus, because it ends up going all under the mesh
Depends on how many things you have covering the ground (rocks, plants, wood, decorations) to say if an undergravel filter is adequate. With lots of stuff in the tank, the filter will easily get clogged and have problems. More information on your tank, and/or a picture would help.
I would add another HOB filter whether or not you get rid of the UGF, cause as previously stated, UGFs just aren't up to par with mechanical filtration, but do wonders with Biological filtration. If you plan on getting rid of the UGF, and add another HOB, keep the gravel filter running with the new filter for a month or so, so it has time to grow some batceria colonies.
I used to run them and let me tell you this. I didn't know to clean them out every year and when I didn't I would get the nastiest algae bloom/green water you have ever seen and I lost all my fish twice because of it. It happens overnight and I changed water 3-5 times a day and couldn't get rid of it.
Now I have run them succesfully though. I did this by heavily vacuuming the gravel weekly and once a month taking a large plastic hose and shoving it under the plates to syphon off the buildup. I have also grown plants on UG filters but they never thrived and once the roots got into the grates the plant most often died.
A good HOB will serve you well and depending on how hard you want to work to get the filter clean an internal could work also. I have seen a stack of sponge filters that actually look kinda cool and could actually work for a 30 gallon. LINK
I actually like undergravel filters a lot, but I like them so long as they're just a bonus. For example, if I'm running an undergravel filter I don't count it in my filtration. Sure it's there, and working, but I still want a HOB that is doing enough for the entire tank (or other means of filtration). Undergravel by itself? I'm not convinced.
UGF's are fine in freshwater tanks, as long as you know how to maintain them. They are more for the dedicated fishkeeper and not for the beginner fishkeeper. If the Chicago Shedd Aquarium uses UGF's in some of their display tanks, then I'm sure it would benifit the home aquarist. Of course, they should NEVER be used for salt water tanks.
The can be maintained and used with very good success if you do what is needed to take care of them. Deep gravel vacs, clean out underneath with a tube once or twice a year, don't overfeed and the basics.
The biggest is the assumption that you never plan to have live plants that need to root deep in the substrate. When plants root on the gravel with an UGF, the roots get into the plates and become feathered because of a massive source for nutrients. It is almost impossible to remove a well rooted plant from an UGF without damaging it enough that it won't require recovery time.
Overall they are just a disaster waiting to happen and require a lot more upkeep than the standard HOB or Canister. They also require 2-4 outlets to run the powerheads, take away space for deep substrate for digging species of fish, will never allow you to use fine substrates like sand or Eco Complete, are about the same price of an HOB to run the same tank. If enough mulm builds up underneath it can and will create a dead spot and create sulfide gas which can kill your fish, can cause a major algae bloom and are a royal pain in neck to replace if one ever gets broken.
I just can not come up with a really good reason to use one except it was given to you and you can't afford to get a different filter. Nor have I been able to find anyone in the hobby that has a good reason to use them over HOB or canisters, except for maybe price in larger tanks but I have also priced this and have yet to find a less expensive filter than an HOB.
Yes they can work, yes they have been known to work very well, but I will never run one again.
BTW, UGF actually do nothing as far as filtering your tank. They take the mulm and waste and the gravel acts as your biological and mechanical filter with all the bacteria in the gravel and very little on the UGF plates. Any waste that gets under the plates is either thrown back into the tank or turns into a dead spot and will cause problems eventually.
HOB and canisters simply give you so many more options to mechanically, biologically and chemically filter a tank whatever way you need to and most importantly, whenever you need to.
Just one last thing, until you can replace the AquaView, I would run both until you can get a secondary filter to assist the AquaView or raplace it with an AC HOB or a better one. Just maintain the UGF as well as you can and vacuum the gravel, very, VERY well weekly.
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