This page contains affiliate links.  All that means for you is that if you click on one of my links and make a purchase, I receive a small commission.  This helps me keep this content 100% free!  But rest assured, I only recommend products I know and trust! Happy Reefing!

Week 11. Common Saltwater Aquarium Beginner Mistakes!

Updated 2023

This week, our focus turns to the frequent and straightforward mistakes that many newcomers to the saltwater aquarium hobby tend to make. We’ll delve into blunders involving equipment, livestock, and everyday habits that can trip up beginners. While we all stumble along the learning curve, steering clear of avoidable slip-ups not only safeguards your progress but also conserves both your resources and time!

This Week's Video:

Common Mistakes By Category

Research and Reviews

  • When you’re doing your research never trust one person or one community (one Facebook group, forum, YouTube channel. This applies more when you are looking up an issue with your saltwater aquarium or asking for advice about advanced things.
  • Don’t get too excited or disregard gear quickly after reading one or two reviews, people who leave reviews are often the minority of hobbyists. Make sure to at least read multiple reviews, but asking in big reefing groups will probably give you a more accurate “gear review”.
  • Reach out to people with a “resume” sometimes that means scientists, but more often we are just talking about people with aquariums that are successful and established. Time in the hobby alone doesn’t make an expert, but a 10 year veteran with a 400 gallon aquarium full of healthy coral probably knows a thing or two! 

Patience and Not Freaking Out

  • One of the things we all as hobbyists struggle with the most is not being overly reactive when we start seeing issues. Most issues in this hobby are not sudden, but rather a build up of bad habits or just something you weren’t aware of. A common phrase we have is that “nothing good in an aquarium happens quickly” so don’t expect to fix whatever issue you have in a day or a week! 
  • Similarly, you have to have patience after you setup your saltwater aquarium, as the biological processes that ultimately make our aquariums successful will take time. Some really dedicated hobbyists will slowly “mature” their tank over the course of a year before they start adding in the corals and other animals that they want. You should expect your aquarium to at least take a month before it is anywhere near the maturity level for a healthy system. 
  • Never put in any animals before the Nitrogen Cycle is complete. We have covered how to check if your cycle is complete before! 
  • Another quick tip is to not constantly tinker with all your gear. Ultimately what you need to do is find a good parameter for all your gear (good lighting intensity/spectrum, filtration protocol, etc.) and stick to that as stability is the number one thing you need to succeed! 

Money and Purchasing Habits

  • This is fairly simple, but don’t underestimate the initial costs of this hobby. It can be way more than you think, but it isn’t an extraordinarily expensive hobby, you just buy most of your gear all at the start. 
  • When buying gear, don’t necessarily trust that expensive gear will always be the better gear for you. Go more based off your goals and reviews of fellow hobbyists. More important is to get reliable gear with a good reputation. Worse than getting unnecessary expensive gear, is going super cheap on important gear. Sure it might work fine for a relatively long time. At best it looks ugly and at worst it is inefficient and will break any minute.  
  • Don’t buy a small aquarium (under 10 gallons) just because it is cheaper. It may seem counterintuitive but such small aquariums require a lot of skill and work to keep stable. If you can’t afford a 15-30 gallon aquarium at the moment, its always better to just wait and save up your money.

Livestock Choices

  • Impulse buying fish or corals as an unexperienced beginner is a HUGE mistake that we all will make more than once. However, it is often a really bad idea if its a coral or fish you have never heard about. Do your research before buying any livestock!
  • When you buy new livestock, its a good idea to do a quarantine protocol (and to have a quarantine setup available). However, make sure you don’t accidentally overdose medicine or use the wrong medicines. 
  • Don’t buy finicky fish unless you dedicate a lot of research and specific gear to them. If it is a tedious fish to take care of, just don’t do it as you will eventually get tired or start slacking. Try to make sure you never accidentally turn the hobby into a part-time job! 
  • As we say a lot, plan out your aquarium well ahead of time and have an idea of the corals, anemones, and fish you can support! We sometimes see hobbyists putting in livestock that won’t fit in their aquarium or won’t be compatible with other animals, which always leads to grief. 
  • Add in livestock slowly if you can, as adding in a ton of animals all at once won’t give your filtration system enough time to react, and may lead to issues. 
  • Finally, don’t overfeed corals and fish, and make sure to vary your food choices. Don’t get cheap food or food in bulk. Getting food in bulk will make it more likely that you will overfeed or it will expire before you use it up. Just like us, these animals need variety in their diet to be healthy and look good. As well, overfeeding (especially with cheap food) will very quickly cause a ton of issues. 


  • The first step in filtering your saltwater aquarium is making sure the freshwater you use to make your saltwater and top off your aquarium is perfectly clean. This means getting an RO/DI filter! There are always exceptions, but in the vast majority of cases we suggest you get one, as it pays off pretty quickly. You could use tap water with dechlorinator, but that is just asking for a ton of issues as you have no idea what else could be in your tap water. 
  •  Overusing chemical filtration and over filtering as a whole. The goal is not to have 0 nitrates or phosphates, just low levels. It is very possible to over filter and cause harm that way. 
  • Not being consistent with your water changes is probably the biggest mistake you can make, as we always say that stability is the most important. A strict water change routine and schedule is a large part of maintaining stability.
  • Finally, make sure you get enough biologically media and get a decent amount of sand (DON’T go bare-bottom) The bacteria mainly lives on “surfaces” rather than the water so you need to have adequate surface area for the bacteria to live on and sand provides a ton of it. 


  •  Having light that is too strong or has too much in the red and green spectrum will make it more likely that you either overwhelm corals and/or cause more algae to grow than normally would. Get a lighting schedule and spectrum from a more experience hobbyist or feel free to reach out to us and we can help! 
  • Only keep your lights on (at full intensity) for at most 8 hours a day, and if your light doesn’t have a built in timer, get a mechanical timed outlet to accomplish a set lighting schedule.

Maintenance and Testing

  • Don’t vacuum your sandbed too much, it may look dirty for a while, but only clean stuff up from the top of the sand, let the sand settle! You can still vacuum it, just don’t do it on a weekly basis.
  • Don’t skip water changes unless you just have to, and try to get it done before or after! 
  • NEVER top off the aquarium with saltwater instead of freshwater! When the saltwater evaporates, the salt remains just the water leaves, meaning your water can become way too salty. 
  • Water changes can be tedious and take a bit of time, but never fully walk away from your aquarium while water is going in or out. There are tons of stories of flooding the house during a water change, or even more scary is drying out your aquarium and killing your animals! 
  • Thoroughly wash and rinse your hands before putting them into your water, especially important in smaller aquariums where any chemicals on your hands could cause issues. 
  • Try not to clean your aquarium glass with strong cleaning chemicals, nor should you spray stuff like Febreze near the aquarium! 
  • Finally, don’t forget to test your water as often as possible! Once a week is preferable but once a month is the minimum. Often, testing the waters are the only way to catch issues and bad trends before they become serious problems and cost you losses! Also, be aware that you may need to test for calcium and alkalinity when you start getting more corals. 

Other Mistakes

  • Don’t use metal fittings and/or hose clamps as they will rust, basically keep metal out of your aquariums. 
  • When making RO/DI water, set timers or other ways to make sure you don’t forget and cause a flood! 
  • When cleaning your glass, watch out for sand particles getting in between, as they can scratch your glass.
  • You can get away without a lid, but if you can, get a lid so that you don’t have to worry about your fish jumping out, or about any other pets jumping in! 
  • Finally, make sure your have good organization. This includes having organized wires of all your gear, keeping your water change gear in one spot, etc. As well, attached your power strip either to the wall or inside the wall of the aquarium stand, so that it isn’t resting on the floor. If there is ever a minor flood from aquarium related things, the electrics will be safer. 
  • Bonus tip: dust and wipe down your gear every once in a while, it will also make you look closely at your gear often so you can catch if there is an issue.