Hi
I do hope no one jumps on me for this post.
Sadly you’re seeing filters as a mechanical thing, if you think bio your get a better understanding of filtration.
It’s better if I ask you to follow this link to understand how your filter works.
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To use a filter to just trap waste from fish is counter productive and could result in a polluted tank.
A filter will try to start a Nitrification cycle this is the term a cycled tank comes from to add an un-cycled filter to a tank is not a good idea. First cycle the filter. To do this get a bucket and fill it with water from the tank and run the filter in or on the bucket for 3 or 4 weeks.
Your filter is ready when your Ammonia reads 0 your Nitrate reads under 40 PPM and your and Nitrite reads 0.
One of the most effective filters is what is called a trickle filter were water from the tank is very slowly passed over a oxygen rich media like “Grogg Glass” the slower the better and the larger the area of media the better, the water absorbs the oxygen as it is “purified” by the massive colonies of bacteria living in the media.
Many years ago it was the only way to keep Discus or marines.
I have seen people build a filter 3 times the tanks size to just keep a few Discus.
A common mistake often made is to equate size of filter to amount of fish i.e. more fish I need a bigger filter.
The controlling factor with fish keeping is the tank size and sadly it works on a form of inverse square rule. A tank holding 4 fish 1” long would need to be 4 times the size to hold one fish 4” long, to understand this look at a 12” fish would you keep it in a tank the same size as you would keep 12 x 1” neon’s in?
Adding fish is also some thing were we don’t take the filter in to account.
Let us take a new tank with 2 fish in it the tank has just balance and is running fine we wish to add more fish say 10 more as the tank is a 4 foot tank and can take it well the tank can but the filter has happily set its self up to handle 2 fish the bacteria in the filter is just right to chomp away at the ammonia from 2 fish when wallop you give it the poo and pee from 12 fish to deal with instant filter crash.
So when adding fish a good rule of thumb is only add the same amount as you have and if you can less.
Sadly so many things affect the fish we keep this is why the successful fish keeper and fish breeder have thought of every angle and dealt with it.
One more point is that despite a power head seeming to be a pure mechanical filter it is not every filter by definition will have some form of biological action even trapped mulm will start a bacteria colony when subjected to water flow and oxygenation.
