If there has been a mysterious death in your aquarium, determine the cause before seeking a replacement.In a nutshell, the reason people are drawn to this hobby (not counting the genetic mutation unique to marine aquarists that I can only assume researchers are close to isolating) is to enjoy up-close-and-personal encounters with exotic marine life. In other words, the whole point of this crazy venture of ours is to acquire specimens for our tanks so we can spend as much of our free time as possible viewing and appreciating them—just as the point of taking up golf is to go golfing as often as possible. But one significant difference between aquarium keeping and many other pursuits is that there are certain times when it’s decidedly not in your best interest to engage in one of the core aspects of the hobby—the livestock-acquisition part, that is.Here are five circumstances in which adding another animal is precisely the wrong thing to do. You’ll notice I’ve targeted this post at beginners, but even experienced hobbyists sometimes forget these points or get impatient and add specimens when they really shouldn’t. 1. Before cycling is complete When cycling a new system, you should observe subsequent spikes and declines in ammonia and nitrite levels and then gradual accumulation of nitrate.