is supported by our readers. When you buy through links on our site, we may earn a commission. Learn more.

Common Mistakes Made By New Saltwater Hobbyists

Owning a saltwater fish tank can be a very rewarding experience. Only those of us that are in the hobby can truly understand how fun and exciting it can be. Even though my family and friends sometimes think I am crazy for spending thousands of dollars and working hundreds of hours on my aquarium, the joy I get out of it is unmeasurable.

After nearly 15 years in the hobby, I have made every mistake there is. Some of them were small, and other not so much. While learning first hand from your mistakes is all part of the experience, taking a few precautions and knowing what your up against can make fishkeeping a lot easier in the long run.

Here is a list of the top mistakes made by novice aquarists and how to steer clear of them!

Not Cycling Properly

Cycling an aquarium is the process of building up the beneficial bacteria that converts fish waste into an non-harmful substance.

When fish waste or uneaten food dissolves in a tank, ammonia is released (EXTREMELY toxic to fish in any quantity). In a properly cycled aquarium, a certain type of beneficial bacteria (which love ammonia) converts this ammonia into nitrite. Nitrite is still toxic to aquarium fish, but not as toxic as ammonia.

So…now we took care of that pesky ammonia, but our nitrite is off the charts. Turns out, there is a second type of beneficial bacteria that feeds on nitrite and converts it to nitrate. Lucky for us, nitrate isn’t too bad! It is still harmful to fish, but only in high quantities and can be kept under control with water changes.

Once these two types of beneficial grow to large enough populations, fish wastes and uneaten food can be converted straight to nitrate without any harmful spikes of ammonia or nitrite.

Cycling your fish tank is the first big hurdle that a reef keeper comes across. It can be extremely difficult to have everything set up, purchased, and ready to go, but not be able to put anything in your tank for months on end. There are several steps that you can take to speed up the process of cycling your reef tank, but in the end it is something that just takes time.

The biggest piece of advice that I have in regards to cycling your saltwater aquarium is this; TAKE IT SLOW. The old saying “you get what you pay for” is true here. While your not actually paying for anything, the longer you let beneficial bacteria build up, the healthier your tank is going to be in the long run. Cycling a tank from scratch can take 4-8 weeks, but it is worth every frustrating day, trust me.

Too Many Fish, Too Fast

I know, it is exciting when your tank is finally cycled. You waited nearly a month for your levels to work themselves out and you can finally add fish! All you want to do is drive over to the fish store and get every fish you had your eyes on.

While this may be tempting, it is important to remember that your tank is still new. The tank may have been cycled properly, but the beneficial bacteria are still building up and too large of a bio-load can overwhelm them. These little invisible creatures are your best friends, take care of them!

For saltwater aquariums up to 50 gallons, I recommend to never add more than two fish per month when starting out. I love clownfish, so when my tank was properly cycled (remember to double check!) I ran out and got two of them and didn’t add anything else for a few months. Make sure to monitor your levels closely during theses first few days and make sure nothing spikes.

During this time, it is also important to feed lightly. Since your fish are new to the tank, they probably won’t eat too much anyway.

Not Enough Water Circulation

Water circulation is crucial in saltwater aquariums, way more so than in freshwater aquariums. In fact, many organisms present in saltwater fish tanks rely solely on water movement for survival. Corals, for example, thrive best in places where the water current is strong and transports food to them.

One of the most important aspects of water circulation in the Oxygen/Carbon Dioxide exchange process. Dissolved oxygen is crucial to a healthy tank, sustaining all living creatures within it. Oxygen enters the water through turbulence at the surface (in nature this is the waves, in an aquarium it comes from filters or powerhead). Without some sort of water circulation or turbulence at the surface, oxygen has no opportunity to dissolve into the water.

As oxygen dissolves into the water through circulation, carbon dioxide is also carried out. Without proper circulation, carbon dioxide builds up, causing you pH to drop and your aquarium to crash.

In saltwater aquariums, powerheads are most commonly used to increase water circulation. Its best not be cheap when it comes to powerheads, but you definitely don’t need to spend hundreds and hundreds of dollars when starting out. A great starter powerhead is the Hydor Koralia. They are powerful, durable, and a great value.

Topping Off With The Wrong Water

When water evaporates from your saltwater fish tank, salt is left behind. As more and more freshwater leaves the tank, the salinity of the water slowly rises. This can kill your precious fish and coral! As a result, instead of adding more salt water to your tank, you should be adding fresh water for top offs.

Surprisingly, the type of freshwater you use for top offs is extremely important. While it may not matter to you whether your water is distilled, purifiers, or whatever else their is, it is very important to your fish.

In a perfect world, it would be best to only use RO/DI water for your fish tanks, but this requires an expensive setup and can be time consuming. For most people, its really not an option.

The second best option for your top offs is Distilled water. You can almost always find this at you local supermarket in gallon jugs. I have personally been using distilled water from WalMart for years and it has been perfect. Never use “purified” or “spring” water. They often contain high levels of dissolved particles and can harm your fish and corals.

Buying Unhealthy Fish

The fish keeping industry has a lot of dirty secrets, some of which are pretty disturbing. Saltwater fish are often harvested by poisoning and electric shock, which takes a huge toll on their health.

Over the last few years, huge efforts have been made to stop this kind of cruelty and a lot of progress has been made. Buying captive bred fish is a great way to ensure that no harmful harvesting techniques were used. Captive bred fish are also much more used to aquarium life and are much healthier in general.

Of course, just because a fish is wild caught doesn’t mean it was poisoned or shocked. Many types of fish are harvested and sold responsibly and fairly. It is important, though, to be able to differentiate a heathy fish from a sick one.

When making sure your potential fish friend is not sick, look at its behavior and appearance. Here is a list of things to look for:

  • Healthy fins (no holes, no deteriorating sections, no large pieces missing)
  • Engages with other fish (a sick fish will often isolate itself)
  • Clear eyes (a fish with cloudy eyes is often a very bad sign)
  • Swims strongly around tank
  • It eats (this is the most important, sick fish will often stop eating. Ask a worker to feed the fish and watch it eat)

Not Keeping Up With Maintenance

Keeping a saltwater fish tank can be a lot of work. To enjoy a healthy aquarium, water changes are necessary and often overlooked by novice aquarists. Water changes of 10% to 20% should be done on a weekly or bi-weekly schedule, depending on the bio-load of your tank.

The first benefit to water changes is the replenishment of necessary trace minerals. In natural sea water, hundreds of minerals are present in tiny qualities, which fish and invertebrates use to stay healthy. It is the same concept as people taking vitamin supplements! As these minerals are used up, they must be replaced, which can only be done effectively though water changes.

Secondly, water changes are necessary because it helps remove harmful toxins. Remember how we talked about nitrate and the cycling process? Nitrate is the final step of the process and builds up in your tank over time. It is not harmful in small qualities, but a lack of water changes can cause a spike in nitrate which can kill your fish. Water changes are an easy way to remove nitrates and keep your fish healthy.

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.

Leave a Comment