There are many kinds of strange stones used in fish tank scenery, and there are no special requirements. You can choose according to your personal hobbies and aesthetics. For example, bamboo shoots, axes, stalactites, Taihu rocks and coral rocks, as well as colored pebbles, reed pipes and magmatic rocks in the south.
It is necessary to find out the types of fish, because the landlord did not specify what kind of fish to raise, so I can only say it in general here. Due to the elemental composition of shells, it is determined that putting shells into water will lead to the alkalinity of water and the hardness will increase slightly. The degree of rise varies according to the number of shells. Simply put, some fish like acidic water, some like alkaline water, and some are more adaptable, so it doesn't matter. Landlords can know what kind of water their fish like, and then know whether to put shells. Of course, it doesn't matter that a small amount of shells beautify the environment and have no great influence on water quality.
If the fish raised by the landlord prefer to rub the bottom or bottom fish, then be careful not to put too big shells to avoid scratching the sad fish, and similar ones, such as corals, should also be paid attention to. It's okay to put a small amount, but it's not good to put too many shells in the sea. It is best not to put shells in the sea, unless raising shells of marine fish will increase the alkalinity of water. It's okay to like alkaline fish, but not acidic fish.