What type of filter do you mean by internal? I know that Americans use different terms for filters from us over here - for example you use the word cannister, we use external for the same filter. Do we mean the same when we talk about internals?
To me an internal filter is one that sits inside the tank completely submerged. This type of filter does not need water pouring in the top of it. I have only ever used this type of filter and an air powered sponge filter; the only time any filter has not turned back on was one particular filter where I had to flick the impeller fins to get it going after every water change.
This is the kind of filter we call internal, this is what I have in my main tank now https://www.eheim.com/en_GB/products/technology/internal-filters/biopower
Apart from external/cannister filters, HOB filters and internals of the type I described, there are also trickle filters popular in the UK. There are located in the hood; water is pumped up from the tank, through the filter than back down into the tank. This type run the risk of drying out during a long power outage.
To me an internal filter is one that sits inside the tank completely submerged. This type of filter does not need water pouring in the top of it. I have only ever used this type of filter and an air powered sponge filter; the only time any filter has not turned back on was one particular filter where I had to flick the impeller fins to get it going after every water change.
This is the kind of filter we call internal, this is what I have in my main tank now https://www.eheim.com/en_GB/products/technology/internal-filters/biopower
Apart from external/cannister filters, HOB filters and internals of the type I described, there are also trickle filters popular in the UK. There are located in the hood; water is pumped up from the tank, through the filter than back down into the tank. This type run the risk of drying out during a long power outage.
