So you have got your Aquarium home, out of the box and filled with saltwater. In all excitement you cant wait to get some fish, so you dash to your local fish shop and buy a pair of percula clown fish. A few days later your pair becomes one, or even worse you lose the pair.
Why? You haven't let your tank go through the Nitrogen cycle. You must do this and wait until Ammonia and nitrite are zero. Wait until Nitrates get to about 0.5ppm. Only then should you start adding livestock.
Stocking too much. We all want a tank full of wonderful colours and life, but you can only keep as many fish as your tank volume will allow. Although this does not apply with Corals and Invertebrates. You can stock as much as your tank will allow but taking into consideration space for your fish.
Stocking too fast. Going out and buying all your stock in one go, is not a good thing to do. It will put too much load on the biological filtration and could wipe about your newly purchased livestock in a matter of days or a couple of weeks. The best advice is to buy one fish per month. This will allow your filtration to deal with the extra load and create the De-nitrifying bacteria. This way you can spread the cost of creating that perfect Aquarium.
Acclimatising fish and corals. You can never spend too much time acclimatising your livestock. I would recommend at least 45 minutes maybe longer. Start by placing the bag in the aquarium let the temperature adjust first, then start adding a small amount of aquarium water to the bag at ten minute intervals. Remember your water parameters are going to be different to the water the livestock has come from. Now you can enjoy watching the Fish or Coral for many years to come.
Research, or lack of it! Don't just assume everything is compatible, it most likely is not. Some Fish eat Corals, some Corals eat Food, some Fish and Corals require different foods. Many Fish could outgrow your Aquarium. Many corals have stinging tentacles and will damage or destroy others. These are to name just a few of the variables, Make sure you can provide what your livestock need.
Money is no object! "I'm going to buy a five foot tank and fill it to the brim with fish and corals" Some people do have the money to do this. Please remember, and take into account the statements in this article. This is a selfish attitude, think of the conservation for these animals and the impact to the environment. Doing this is irresponsible, Please if you have the money, take it slow and enjoy this fascinating hobby.