Algae Pads

I'm not sure about algae pads - does yours say how it is supposed to work? I think some of them absorb things like phosphate which is often blamed for algae. Whether they work or not I can't say as I've never used them.

Carbon pads I do know about. Carbon is a hangover from decades ago when the nitrogen cycle was not understood. Fishkeepers did water changes very infrequently (they thought they were bad for fish) and the water turned yellow because of the build up of organic chemicals. They didn't like the yellow so they used carbon to remove it. My parents had a book on how to do household repairs dating back to the 1970s and in the section on aquariums, the filter it showed was a box containing carbon covered with a layer of filter wool to keep the carbon granules in place, powered by an air pump.
We now know about the importance of water changes and having bacteria in the filter so we don't actually need carbon on a routine basis. The main uses for carbon are for removing medication after treatment has finished and removing the brown colour that comes out of bogwood.

Carbon gets full in a few weeks and stops adsorbing things. If you need to adsorb things, it must be replaced regularly - and filter manufacturers say to replace it because it is cheap for them to produce so brings in a nice bit of revenue if everyone changes it every month.
You can either leave it there permanently or get rid of it and replace it with a sponge or a layer of filter wool/floss (which isn't a very good home for the bacteria but is good for removing the fine particles that pass right through a sponge).
There is one danger with leaving the same carbon pad in the filter permanently. If something enters the tank that is more strongly attracted to the carbon than the usual chemicals which will be attached to it, there is a danger that this new substance will displace what is on there now and stick to the carbon in its place. If this new substance is a medication, it will be removed from the water and won't work. The risk may be small, but it exists. Removing the pad just in case will also remove a fair chunk of the bacteria, which will have colonised a pad that has been in the filter for months.


I have not used carbon on a routine basis for years, not since I discovered this. But I do have a pack of carbon granules and a small internal filter in the cupboard for whenever I do need to use it.