1. Stop Chasing Numbers

Stability is king and when it comes to parameters, stop trying to chase down a particular number. Instead, maintain stability within a suitable range and be satisfied things are stable. In most scenarios, your test kits are not accurate enough anyway, so constantly trying to drill down parameters to a specific number often leads to instability. If you're having to continually make adjustments to parameters, you're doing something wrong. Water changes and daily supplementation should maintain stability in your tank without needing to make constant adjustments. 

2. Stop Overfeeding

Everyone does it, nobody wants to admit it. This is hands down the #1 problem for aquarists, not only for saltwater reef tank owners but freshwater aquarists too. It's just really easy to feed too much and since most of us enjoy feeding the fish, we like to do it all the time.

It is best to break up your feedings into multiple smaller feedings throughout the day using the appropriate amount of food. Also, feed just a small pinch at a time and watch your fish consume it, then feed a little more. The goal is for the fish to eat the food and avoid allowing food waste.

3. Don't Run Your Lights Without a Timer

While it might seem silly, some hobbyists refuse to use a timer on their aquarium lights. For whatever reason, this needs to stop because most LED lights come with a timer built right into the fixture and if you're using T5s or some basic LEDs without a timer function, a classic timer can be found for under $25. 

4. Stop Using a Calcium Reactor AND 2-Part Solution

There is no need to use both a 2-part solution and a calcium reactor at the same time. It is best to choose one and combine it with Kalkwasser instead should you need to. 

Gorgonian

5. Don't Listen To Everyone

While it's a difficult thing to master, it doesn't really have to be. Choose a mentor who has achieved the kind of success you wish to achieve in your tank and stick with their advice. Don't attempt to blend advice from different people to come up with what you think is the best approach.

6. Stop Using Old, Dangerous Equipment

Neglected equipment is not only unreliable but can also be dangerous. Saltwater can wreak havoc on electronics and other equipment used around your aquarium making it all that more important to maintain. This is especially true for heaters, lighting, and pumps. 

7. Stop Cleaning Your Water Too Much

Can there be too much of a good thing?  In the case of filtration and maintenance, Yes. Protein Skimmers, filter rollers, refugiums, algae scrubbers, and various other techniques we use to keep our aquarium water clean is all fine and good until you reach the point at which your water is too clean. In this case, nutrients get stripped from water leaving nothing behind for the organisms inside your tank. Be mindful of it and understand that you probably don't need to employ more than a handful of techniques to get the job done.   

8. Stop Adding New Fish Without Quarantine

The process of quarantining new fish helps dramatically reduce the risk of introducing disease and parasites into your aquarium.  If you do not quarantine your fish at home, consider sourcing your fish from reputable retailers who offer this quarantine service. While you will pay a premium for previously quarantined fish, you can be confident you're not going to introduce harmful pathogens into your tank.  

Tang

9. Stop The Dump & Pray Approach

Research is incredibly important for choosing the right fish for your aquarium. It's easy to get excited and purchase an impulse fish but do your best to control those impulses so you can be confident ALL of your fish will survive and get along in your aquarium long term. Don't just blindly buy fish and dump them into your aquarium hoping that everyone will get along. Consider using an isolation box in your display which is a very effective approach for acclimating new fish into your existing population.  

10. Poor Coral Placement

Coral placement is incredibly important for the long-term health of your reef. Not only should you consider the lighting and flow requirements of your corals but also consider how one coral might affect its neighbors. The growth pattern and aggression are very important because corals can easily shade one another or sting each other in a fight over real estate. 

11. Stop Feeding Romaine Lettuce

Romaine lettuce does not grow in the ocean and is not a suitable source of nutrition for your herbivorous saltwater fish. Use foods that contain seaweed and spirulina instead.