Hi and welcome to the forum
What are the tank dimensions (length x width x height)?
What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Depending on what the GH of your water is, will determine what fish you should keep.
Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.
If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.
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Avoid dwarf gouramis (Colisa lalius) and all their colour forms. They are regularly infected with the gourami Iridovirus and or Fish Tuberculosis (TB). Neither of these diseases can be treated and once they are in your tank, they are there until to strip it and disinfect everything.
There are plenty of small gouramis that are less likely to carry these diseases. They aren't as bright and colourful but are generally much healthier fish. Look at Indian banded, sparkling, honey, and licorice gouramis.
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Neon tetras are poor quality and inbred, same as guppies and dwarf gouramis. There are lots of small tetras but it depends on what you like, as well as tank size and water chemistry.
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Blue rams can be good quality or bad. The German blue rams are simply blue rams bred in Germany. They are the same species of fish from Asian fish farms, just bred in a different country. The fish bred in Germany are usually better quality and have fewer diseases than those bred in Indonesia, China or other places.
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What filter media does the AquaClear have in it?
They used to have Ammogon/ Zeolite (white granules used to remove ammonia).
Carbon (black granules used to remove chemicals from the water).
White Ceramic beads designed to hold bacteria.
A sponge to trap gunk and hold bacteria.
If it has carbon or Ammogon in, take these out because they aren't needed. Replace them with another sponge.
Power filters should be cleaned at least once a month. However, if the filter is less than 6 weeks old, do not clean it. Wait until after that before you start cleaning it so you don't disturb the beneficial filter bacteria growing in the filter media/ materials. When you do clean the filter, simply wash/ squeeze out the filter media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn.