Just double-click on the parts, sponges, fish, accessories, etc. and add them to the room above and drag around to arrange.
There are many features to choose from. You can rightclick objects and bring them to the front or delete them if necessary. When you have finished your fish tank, just click the "Save & Download" button.
Please note, that you need to wait until all the pictures are loaded before you can double-click objects. This can take some time, be patient
EDIT: The saved picture doesn't look very colorful, so if you want to keep the colors, you can push the "print screen" (PrtScn) button, then open Paint, push Ctrl + v buttons to paste it, and the save it.
Have fun
Create your fish tank
There are many features to choose from. You can rightclick objects and bring them to the front or delete them if necessary. When you have finished your fish tank, just click the "Save & Download" button.
Please note, that you need to wait until all the pictures are loaded before you can double-click objects. This can take some time, be patient

EDIT: The saved picture doesn't look very colorful, so if you want to keep the colors, you can push the "print screen" (PrtScn) button, then open Paint, push Ctrl + v buttons to paste it, and the save it.
Have fun

Create your fish tank