Chapter 4: Top-Off Mistake You Don't Want to Make

     Okay, so what's this crazy talk about top-offs? What is a top-off and how does it differ from a typical water change? Well I'll get into all of that, but the first order of business when you've got your first round of saltwater in your tank to get it cycling is to top it off with water.

So what does topping off your tank do besides adding water?

     Good question! Topping off your tank helps to maintain your water parameters. This is essential in mitigating the level of stress that you put your livestock through. It also ensures healthy growth and propagation of your corals.

     But that's just the beginning! To effectively top off your tank, you'll want to make sure that you're using the correct water. Water is water, right? Wrong. If you haven't been told already, you should, at all costs, avoid using regular old tap water unless your water level has gotten so low that your fish absolutely need it! Tap water contains chemicals, metals, and other matter that can be harmful to your livestock. If you must add tap water, it's a good idea to use some type of dechlorinator as a supplement.

What type of water should I use?

     For top-offs only, you should be using RO/DI filtered FRESH water. Not salt. Fresh. Many, many folks, including myself, make the mistake at one point or another of topping off their saltwater tank with saltwater. Makes sense, right? But don't be fooled! This can be very dangerous over time. It sounds about right at first, but think about it this way... When the saltwater in your tank evaporates, only the water evaporates. The salt remains, which is why your salinity level can rise if you let your water level drop too low. This is where an auto top-off system can come in handy! Also, RO/DI water can usually be purchased at your local fish store.

Here's a typical RO/DI unit which is used to filter tap water for use in aquariums. Image courtesy of

Here's a typical RO/DI unit which is used to filter tap water for use in aquariums. Image courtesy of

Remember this: Water changes will be conducted with SALTwater

     While regular evaporation keeps the salt in your tank, water changes directly remove the water along with the salt. I'll get more into water changes in the next few chapters, but ensure that you ingrain the difference between your normal top-offs and your water changes in that noggin!

     Four weeks in and we're rockin' and rollin', guys! My goal is to ensure that I cover as much as possible to get you started on the road to success with your reef aquarium. If you've got any additional advice pertaining to top-offs or water changes, I encourage you to leave a comment below. And be sure to tune in next week when I talk about the Nitrogen Cycle.