Firstly this is in no way the finished article. I have lots more I would like to add but finding reliable and verified data is proving quite difficult. Some of the information listed below is my personal opinion. Some of it is taken from other peoples articles and then checked against a different article so that I can verify the information. Some of the information is taken directly from manufacturer websites and probably most importantly some of the information is just someone's opinion. If anyone can add to or dispute anything below please dive in ! It's all about spreading the word and hopefully giving us enough information to make informed decisions.
I believe the 10 times rule for filtration is one of the most misunderstood rules in fish keeping. Each filter needs to be looked at individually with regards to max output, actual output, capacity for media and whether you want mechanical, biological or even chemical filtration to be you secondary method of maintaining your parameters (Primary method being regular large water changes). 10 times is what you need to aim for if you are using a single filter for MECHANICAL filtration and this rule also applies to most HOB/Internal Filters. 4 times is the optimum rate for water to pass through your media if you are using a single filter for BIOLOGICAL filtration although 4-6 times per hour for a large canister filter is accepted to be the recommended flow rate. For biological filtration you will need a slower flow rate and a larger capacity for media. For mechanical filtration you need a faster flow rate and can get away with a smaller capacity for media.
Before buying a filter or multiple filters for your tank you need to look at some other factors. These are –
1. Temperature that you will be maintaining in your tank.
2. PH of the water that will be in your tank.
3. Amount of fish you will be keeping and expected bio load.
4. Oxygen within the tank water.
5. Filter media you will be using.
6. Probably most importantly the actual output of the filter. Most manufacturers do not tell the whole story.
To look at how these factors will affect how you choose a filter I will look at each one in greater depth below.
Temperature – The single biggest factor affecting the growth of Nitrifying bacteria is temperature. Beneficial Bacteria function the best between 77- 86F. BB growth rate declines to 50% at a temp of 64F and there will be no growth at a temperature of 39F. At temperatures exceeding 95 degrees the bacteria start to struggle. The bacteria will die at temperatures below 32F and above 120F. Nitrite oxidizing bacteria are more susceptible to temperature extremes than are the ammonia oxidizing bacteria. Outside these optimum temperatures adding mechanical filtration can compensate for decreased bacteria functionality.
PH - has a significant effect on beneficial bacteria. At a pH below 6.5, they become inhibited and cease being efficient in oxidizing ammonia and nitrite. Maximum rates of nitrification occur at pH values above 7.2, with optimal nitrification occurring around 8.3. At a pH of 8.3, nitrifying bacteria operate at near 100% effectiveness. At a pH of 7.0, their efficiency drops to less than 50%. At a pH of 6.5, it drops to 30%, and at a pH of 6.0, it drops to 10% optimal efficiency.
BIO LOAD – When looking at the filtration that you require you need to factor in the fact that your fish will grow and the amount of waste that they produce will increase significantly over time. 4 small fancy goldfish in a 55 gallon tank will initially produce very little ammonia and your water changes and BB's will easily keep this in check. As these fish grow however, the amount of waste that they will produce can get to the point that your filter will struggle to cope. You may then need to readdress your water changing routine and possibly add extra filtration.
OXYGEN - The minimum concentration of dissolved oxygen required to support effective colonies of beneficial bacteria is 2 ppm. No article on filtration can be complete without mentioning the beneficial bacteria that exist in our tanks. The two main types of bacteria that will exist in a healthy aquarium are
Autotrophic Bacteria – These are the BB's that convert ammonia to nitrite to nitrate (Nitrosomonas Marina and Nitrospira)
Heterotrophic bacteria – These are the BB's that break down solid waste (uneaten food/fish poop) into ammonia.
Both types of bacteria compete with each other as well as our fish for oxygen. Autotrophic Bacteria require a higher content of oxygen than the Heterotrophic bacteria. However, Heterotrophic bacteria are the most prolific consumer of oxygen in our tanks and can even consume more oxygen than our fish !
MEDIA – This can be a major factor on how well your filter will work in relation to your bio load. Some media work better than others. I am a big fan of Eheim Substrat Pro and Efimech. They are expensive but are considered by many to be the best custom media on the market.
1 single ceramic ring with pores (not the smooth kind) will possess a surface area equivalent to 1" of pea gravel in a 10-gallon tank. Just as autotrophic bacteria compete with heterotrophic bacteria for oxygen, they also compete with heterotrophic bacteria for space. Large surface area = more BB's = better biological filtration.
Actual outputs of Canister filters as stated by the Manufacturer
A What the box says – LPH
B What the box says – US GPH
C What will actually be going into your tank – LPH
D What will actually be going into your tank - US GPH
MODEL A B C D
105 480 126 330 87
205 680 180 420 110
305 1000 264 710 185
405 130 343 850 224
106 550 145 360 95
206 780 206 510 135
306 1150 303 750 198
406 1450 383 940 248
FX5 3500 924 1991* 525*
*Independent test results
MODEL A B C D
Classic - 2213 440 116 390 103
Classic - 2215 620 163 510 134
Classic - 2217 1000 264 790 208
Ecco - 2232 400 105 280 73
Ecco - 2234 500 132 350 92
Ecco - 2236 600 158 420 110
Pro - 2222 500 132 400 105
Pro - 2224 700 184 500 132
Pro 2 - 2026 950 250 650 171
Pro 2 - 2028 1050 277 750 198
Pro 3 - 2080 1700 450 1207* 318*
*Independent test results.
MODEL A B C D
XP 1 950 250 530 140
XP 2 1150 303 630** 166**
XP 3 1350 356 730 192
XP 4 1700 450 960 253
**An independent test showed that the XP2 once filled with media and pumping water vertically 1.2 meters actually only managed 350 lph (92 gph). This is significantly less than the 1150 lph stated on the box. Only 33% of actual stated output. The owner then tested the filter with no media and only 8 inches of tubing pumping water horizontally. The filter only managed 900 lph and not the 1150 lph that was expected.
I have only listed the 3 main brands of canister filter just now as details of max/actual outputs on some of the other brands is proving quite tricky to track down. I do intend to try and capture data on AquaEl and Tetratec EX canister filters so watch this space.