How to Decorate My Tank?

How do I know which one of my fishes like lights and which one like shadows or darker environments?

Most common aquarium fish are raised in aquariums or shallow ponds, so they are accustomed to light. Since the tropics get 12 hours of daylight year round, many aquarists use a 12 on/12 off routine. Lighting is not a very important issue for fish, but it is for live plants. Each plant has its own light requirements, so a little research will save you from buying the wrong plants. You can also mix plastic plants with an easy to grow floating plant like hornwort.

Most fish like to have hiding places, so an aquarium needs a fair amount of plants and/or decorations. What kind of fish do you intend to put in your aquarium?

I like to keep fishes in schools
mainly
Tiger barbs/Green Tiger barbs/neon tetras/
also mully/guppy/angels and severom
i do not dare to keep fishes like oskars
thank you my knowledgable friend
peace

You do not want to keep all those varities in one aquarium. They will not get along. Neon and cardinal tetras will school if you have at least six of them. Fish selection depends on the size of the aquarium and the habits of individual fish species. A good place to start is a 15 or 20 gallon aquarium with a single species like guppies. They're very colorful and relatively easy to care for. Something like angelfish are more difficult to keep, and they need lots of space. What size aquarium do you have?