When performing maintenance on your aquarium, it’s easy to walk away for a few minutes and forget that you have turned pumps off and have probably closed off a few block valves. While it’s ok to do these things, it’s very important to remember to turn pumps back and on and make sure all of the valves are open. If a pump is on while the valve is closed, then the pressure could cause plumbing failure and leaks, to say the least. Powerheads that are shut off for long periods of time may become the unintended home for various livestock, and we all know you don’t necessarily want to remove a fish’s residence. When they are turned back on, the fish can become mutilated or likely killed.