You can most certainly put river rocks in your fish tank! In fact, many people believe that river rocks can provide a more naturalistic look for your aquarium. Not to mention, fishes love hiding in and around the nooks and crannies of these rocks. However, there are a few things you need to take into consideration before adding river rocks to your fish tank.
For starters, you need to make sure that the river rocks you select are safe for use in an aquarium. Some types of rocks can release harmful toxins into the water which can be detrimental (and even deadly) to your fishes. So, be sure to do your research and only select river rocks that are known to be safe for aquarium use.
Another thing to consider is the size of your river rocks. You'll want to avoid any rocks that are too large as they could potentially damage your fish tank (or injure your fishes). Instead, opt for smaller-sized river rocks that won't pose any threat to your tank or its inhabitants.
Finally, when addingriver rocks to your fish tank, be sure to rinse them off thoroughly first. This will help remove any dirt or debris that could contaminate your aquarium water. Once they're rinsed off, you can then go ahead and add themto your fish tank!