Hi and welcome to the forum
Filters should be cleaned at least once a month and every 2 weeks is better. However, if the filter is less than 6 weeks old, do not clean it unless the flow rate is reduced.
If you have a power filter, you wash the filter media/ materials in a bucket of tank water and when they are clean, put them in the tank. Then wash the filter case and impellor (magnet with plastic blades) under tap water. When it's clean, put the filter media back in the filter, fill the filter up and get it running again.
If you have a filter that says you need to replace filter pads every couple of weeks, you can put some sponges in the filter and clean them as described above. I use AquaClear sponges but there are plenty of other brands. Just use a pair of scissors to cut them to fit.
You can get round/ cylindrical sponges for some brands of internal power filter. These sponges have a hole through the centre of them and they fit over the intake strainer of most external power filters. They act as a prefilter and reduce the gink getting into the motor, and they hold beneficial filter bacteria.
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You should do a 75% water change and gravel clean the substrate every day for a week, and then once a week after that. Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
You do water changes for 2 main reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.
Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.
If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.
Imagine living in your house with no windows, doors, toilet, bathroom or anything. You eat and poop in the environment and have no clean air. Eventually you end up living in your own filth, which would probably be made worse by you throwing up due to the smell. You would get sick very quickly and probably die unless someone came to clean up regularly and open the place up to let in fresh air.
Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and makes the environment cleaner and healthier for the fish.
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Green Cloudy water is caused by single celled plants called algae. They grow from excess light or excess nutrients, sometimes both. Adding live plants can help, as can reducing the lighting period and doing big daily water changes.
Milky Cloudy water is caused by a bacterial bloom, which is normally caused by uneaten food rotting in the tank, or a filter that is not working properly.
Cleaning the filter (as described above) and doing big daily water changes for a week will usually fix both of these issues.
Don't add any new fish for a month so the tank has a chance to settle down.
