The Basics of Setting Up a Goldfish Tank- Filtration
As mentioned in the previous section: The Basics of Setting Up a Goldfish Tank- Tank Size, goldfish are very messy and have high ammonia outputs so a powerful filter is a must. Filters hold beneficial bacteria which live on the filter media and convert the ammonia into nitrites and then to nitrates. In order to do this you want a lot of media for the bacteria to colonize and preferably a flow rate of 10x the gallonage. So if you have a 40gal tank you want a filter that has a GPH(gallons per hour)of at least 400gph. This is the standard rule for HOB(hang on back) filters. If you decide to use a canister filter you can go as low as 7x filtration; this is because the water although moving more slowly through the canister is coming in contact with much more biomedia and therefore more waste is being processed and removed/changed. This article will be a very basic rundown of the two main types of filtration available commercially and the pros and cons of each.
Canister vs. HOB Filters:
If you're new to the hobby you might be thinking; What is a canister filter? Simply put a canister filter is a large container filled with various stages of media that tank water is passed through. It typically relies on gravity and suction, via an impeller, to draw water down into it and must be lower than the tank to function properly.
The benefits of canister filters are that because they are placed behind and below the aquarium they offer much more space for filter media. This increases the amount of beneficial bacteria the filter can hold and therefore maximize biological and mechanical filtration. Canisters also offer tons of customization options for media combinations. For example you could have two canister filters on one tank, and pack one with ceramic noodles and loose sponge to hold as much biological potential as possible. Then you could decrease the flow rate in that filter so that the water is filtered more thoroughly. Meanwhile the other filter could be filled with water polishing sponges and other things that handle mechanical waste filtration. Canisters are also very quiet.
I don't really see many cons for canisters. They can leak everywhere if not properly sealed or assembled so I place mine in trash bags or in small stylized trash cans in case they overflow or leak. However, I've never had this happen, but better safe than having 55 gallons of water slowly leak onto the new carpet. They can be hard to open when you need to clean them, but I find them very easy to move and I just open them in the bathtub so making a mess isn't an issue.
The most popular canister brands are Fluval and Eheim; but I have only owned fluvals and have nothing but praise for their products. I have a Fluval 306 and a 305(the previous model to the 306). They both look nearly identical and function nearly the exact same. They have lots of room for media customization and are easy to disassemble and clean. I clean my canisters out well bi-monthly if I'm below stocking levels, and every 3-4 weeks if I'm at or above recommended stocking levels.
HOB Filters are the other popular choice. HOB stands for Hang On Back, and are the most common way of filtering any tank. They have an impeller that draw water up the intake tube and through the filter media that is held in the section that hangs off of the tank, then it flows back into the tank.
Aquaclear filters are my personal favorite, because they can hold a lot of media and typically have a high gallonage per hour rate. The pros of HOBs are that they do not take up as much space as a canister and can be moved around easily. They are said to be easier to clean but I found I had to clean them more frequently (bi-weekly) than my canister which I clean monthly or bi-monthly.
The cons are they look more obtrusive than a canister which can sit below the aquarium. They can overflow if not maintained properly or if you stuff them with too much media. They also tend to be noisier, especially as the impellers start to get old.
I find that on bigger tanks (29gal +) HOBs can get especially large and bulky, so for larger tanks it tends to make me lean towards canisters. I also enjoy the amount of customization you get with layer different types of media in a canister filter.
These are really your two best options for filtering a tank for goldfish, as they are very high waste fish and can get quite large. Neither one is better than the other, in the end it boils down to personal preference. Other filters like sponge filters are only effective for quarantine and for raising fry, as they only provide biological filtration and at a lower rate. So they should only be used in scenarios where the fish are receiving large frequent waterchanges. Under Gravel filters should never be used as they are hard to clean which can lead to bacterial issues. In my opinion they are archaic and I can't see them being better than other options we now have.
I hope this article is of some help to you! If there is anything that wasn't covered that you'd like to see added please let me know and I'll put it in. :)
Filter diagram credit to FiltersFast. They will be replaced with my own images when I get the time!
