The first thing you need to do to raise fish is to raise water.
If you like to raise grass tanks, and if you have the time to spare, you can buy some substrate, fertilizer, and grasses, and then you can make a standard grass tank.
You can raise some group swimmers, such as the red-nosed scissors and red and green lanterns, such as Paulownia lanterns, which are effective with lighting. If you want to raise large fish, then remove the center barrier, remove everything inside, and raise some maps, parrots, and so on. As long as the temperature, water quality, and filtration system are met, these fish are still easy to raise. If you want to raise turtles, a small tank would be good too... If you want to keep a turtle, a pig-nosed turtle is a good choice, but it's best to mix it with larger fish.