Undergravel Filter; Pros and Cons

[PineHill]

I was once told that an undergravel filter was the way to go because of the natural bacteria it allows which breaks down waste and helps the nitrogen cycle.  Although I recently read a few posts that said they're not the greatest.  I was hoping that someone could help inform me as to why they're not great and what they actually do.  Also what would the replacement be for my undergravel filter's function?  Thanks again.

Chris

[babblefish1960]

I do recall that in the 1970's, undergravel filters were the way to go as we had just begun to understand a little more about water chemistry.  If you recall, or perhaps your ancestors may, there was no ammonia until about the early 1960's, before that, well, fish deaths were simply unexplained.

The advent of the advantage of UG filters were that it was discovered to contain bacteria that was beneficial to new things like the nitrifying cycle, though that was not exactly understood then the way it is now.

The problem became, that as a UG filter aged, it accumulated a lot of crud that could not be broken down nearly fast enough, and when your overfed tank was old enough, it actually produced hydrogen sulphide amongst other things under there, that could only be dealt with by tearing down the tank.

I found them to be a pain with plants as well, I would begin to see roots emerging from the exhaust tubes, and upon the teardown of one particular tank, I discovered small fish in the plates that had been missing for many months.


Alternates to UGF's would be externally mounted biowheels, fluidized beds, and my favourite recommendation the canister filter. The canister filter can be customized in content and can be changed as you go along.

I tried to keep this short, I hope I answered some aspect of your questions.

[babblefish1960]

One major fault with an undergravel filter that I omitted to mention, the beneficial merits of their bacteria beds are completely subverted by the digging of certain fish, the digging fish obviously. Whenever the gravel would be swept away from the plates of these digging fish, it is surprising just how many of these fish there are, the bacterial activity would stop and become anaerobic where the flow was suddenly lessened.  A big consideration for cichlids of all kinds, as well as loaches, not to mention quite a few others.

[kennyman]

Being a wee lad in the 70's my first big boy tank was a 20 complete with the latest in filtration. A Under Gravel Filter! Every year I had to take the tank down to clean under the plates because, bacteria or no, there was still a great deal of sedimentation happening under there. It was THE worst part of keeping a tank. I would use a corner bubbler or sponge over the ugf anyway.

The only upside was no clutter in the tank or behind it and a nice trickle of bubbles from the heads. I Guess there is always the option of reverse flow powerheads to clean under the plates but meh!

Now that I have begun using natural substrates backed up a a small canister filter I will not likely use anything else.

[PineHill]

Thanks for all the info guys, it really clarified a few things about UG filters. 

So alternatives that were mentioned were externally mounted biowheels, fluidized beds and canister filters.  I've obviously heard of biowheels and canister filters, but not fluidized beds.  I do know the basics behind the canister filter being that its not very complicated but I would benefit a lot if I could get an explanation about the chemistry behind all the working parts of it and as well with biowheels and a fluidized bed. 

Also which one would be the best based on obvious traits (easiest to maintain, cheapest, hardiest, quietest, etc.).  Thanks again, it will make a lot of difference when I set-up my new tanks in the next 5 months.

[babblefish1960]

Hands down it would be the canister filter, you would only really need to rinse it out every six months or so, the bio wheels, well, I have never cleaned one in all the years I have used them, I have them piggy backing the exhaust of my canister filters, so it is always cleaner water.

Fluidized beds are very good biological filters, however, they are not inexpensive, and incredibly fiddly to get the flow just tickety boo so that the entire sand column is working, but not being washed out into the tank.  It really depends what you like, less maintenance, or more exclusive bells and whistles for the snooty factor.

[kennyman]

Trickle filter systems are pretty top notch as they employ large space to oxygenate the bacterial activity. There is a DIY article in the library here that Bruce wrote on his trickle/sump system. He also uses a canister for backup though 

If you are setting up a big display tank a trickle sump might be nice as you can remove all the equipment from your tank and skim the surface of the display with the overflow. Basically your tank has a pipe or overflow box that exports any water in the display over a certain height into the trickle/sump where it is filtered, heated, toped off and then pumped back into the tank.

[PineHill]

I'm also leaning towards a canister filter due to the easy maintenance and all the excellent things I've heard about them.  And babble could you explain what you mean by having the biowheels in combination with your canister?  If that work well for you and provides cleaner water I would probably like to give it a shot as well.

I would ideally like to have less maintenance and less cost, so a fluidized bed sounds a bit expensive, more complicated and more hassle, which are three things I'd like to avoid for now, being a working student.

However I am setting up a big display tank in my living room and the trickle sump sounds good since I have a large stand that could house a sump under the 125 gallon.  I'm also new to the knowledge of sumps and only know a few basics ( no extra junk in the tank, heaters, filter hidden int he sump, etc.).  If someone could help explain the general idea of a sump and go into the more complicated areas that would be awesome.  Thanks.

Chris