Tenji is pleased to present a series of exclusive articles for Reef2Reef members. We will be delving into the various aspects of reef keeping, focusing on tried and true methods that can be implemented by aquarists of all levels. _____________ As a young aquarist working in a local fish store I had a 16” lionfish launch itself out of a tank during feeding time. I quickly placed the fish back into his home, and after a couple hours, the animal returned to normal behavior. However, that event changed my views on the potential for fishes to jump forever. How often do we see threads titled, “Which fish for open top aquariums?” The truth is that every fish has the potential to jump, even the frumpy frogfish. Think of a top as a seat belt for your fish. If you’re serious about keeping your fish friends thriving long term a top is not optional, it is a necessity. Choices for nice aquarium tops run far and wide nowadays, including some that even look great on rimless aquariums. Here are the basic options along with their pros and cons. Glass/Acrylic Top Pros · Readily available · Oftentimes included with mass produced aquariums · Affordable · Keeps evaporation to a minimum Glass/Acrylic Top Cons · Water condenses which negatively effects light penetration · Does not afford high levels of gas exchange · Must be frequently cleaned · Breakable (glass) · Heavy (glass) Eggcrate/Light Diffuser Top Pros · Readily available · Easy to alter shape/size · Affordable Eggcrate/Light Diffuser Top Cons · Many small reef fish can jump through holes · Breakable · Becomes brittle over time · Best used as a temporary top · Uneven light distribution (it is used to diffuse fluorescent lighting after all) Screen Top Pros · Affords superior gas exchange · Best light penetration option · Rarely if ever requires cleaning · Can be custom made to fit within rim of trim-less aquariums (looks beautiful) · Capable of complimenting an aquarium rather than detracting · DIY potential using store-bought material Screen Top Cons · Custom acrylic framed options can be expensive and have long lead times · Screen can be fragile, but is easily replaced · If screen hole not sized appropriately fish can get stuck That’s our lowdown on tank top options. Of course, there are a few exceptions when it comes to aquariums with enclosed canopies, flip-up tops on all-in-one nano tanks, etc., but the fact remains that all fish have the potential to jump, so do them a favor and provide them with a safety net.