Reef Tank: 15 Helpful Answers You Should Know (For Beginners)

Having a reef tank is the closest thing a person can get to having their little marine ecosystem in the comfort of their home. A reef tank would consist of various marine life such as corals, invertebrates, fish, and the like.

But is it easy to own a reef tank? Do you need lights to sustain life? Do reef tanks need filters? Or can one do too many water changes?


Can You Do Too Many Water Changes In A Reef Tank?

Yes, you can have too many water changes in a reef tank. Too many water changes would disrupt the balance of a reef tank, meaning, the pH levels and temperature in your reef tank would always vary, and that would be detrimental to your tank inhabitants.

Not to mention, beneficial bacteria are also at risk of being washed out of the tank due to too many water changes. If you want to avoid harming your marine life, ensure that you follow the proper frequency of changing the water of your reef tank.

So how often should you do water changes to your reef tank? According to an Environmental Engineering aquarist, 10 to 15 percent of water should be changed once every week. This is to safely keep your tank water clean without disrupting the balance of chemicals in the water.

Of course, the frequency of water changes will vary per tank setup. Let’s say your tank has an automatic water changer installed, this would mean you wouldn’t have to change your tank water too frequently. With aid coming from filters and automatic water changers, the frequency between water changes would vary and become less frequent.

Does A Reef Tank Need A Filter?

Yes, reef tanks need filters because, unlike fishes, some corals can’t withstand chemicals in tank water like nitrates and phosphates. The filter’s job would be to remove said toxins to keep corals safe.

Several types of filtration can be used for reef tanks, please refer to the bullet list below:

  • Biological filters
  • Under gravel filters
  • Protein skimmers
  • Canister filters

Each filter varies and has its pros and cons, so it would be entirely up to you on which filter to install in your reef tank.

If you’re having trouble choosing which filtration to choose, we’re here to help you out! Arguably, some of the best filtration systems for reef tanks are canister filters, fluidized bed filters (recommended for planted tanks only), and protein skimmers.

The type of filtration system that you should avoid using would be the wet/dry filters. Aquarists advise against using this type of filter because it’s a nitrate factory and we all know that nitrates are not good for reef tanks.

Is High Magnesium Bad In Reef Tanks?

Some aquarists claim that high magnesium levels don’t have any harmful effects in reef tanks, however, it’s best to stay within the recommended level of magnesium which is between 1250 and 1350ppm.

Truthfully, aquarists should be more worried about having low levels of magnesium because these are detrimental to planted reef tanks. For those of you who have fish-only tanks, you shouldn’t worry about magnesium since these fishes don’t heavily rely on them.

On the other hand, coral-only reef tanks will suffer from low levels of magnesium and this would result in several issues that are commonly faced by aquarists. Such issues are the precipitation of calcium carbonate.

The appearance of calcium carbonate is similar to snow and this sticks to aquarium accessories such as pumps, heaters, and impellers. Without proper levels of magnesium, there’ll be excess calcium carbonate, and corals and other invertebrates won’t be able to build their skeletons.

What Is The Best Temperature For A Reef Tank?

75-78 degrees Fahrenheit would be the best temperature for a reef tank. However, it would be better to know the origin of your corals and know what temperature they’re used to in the wild if you want a more accurate temperature for your reef tank.

Be wary of low and high temperatures in your tank since high temperatures would not be suitable for some species of fish while some corals would prefer a higher temperature. If you’re facing this kind of dilemma, it would be best to keep your fish and corals in separate tanks.

If you’re keeping a reef tank with mixed corals the best temperature would be 77F but if you’re keeping a reef tank with large polyp corals (LPS) it’s best to keep the temperature a bit lower (75F). If your reef tank has more soft polyp corals (SPS) you can make your temperature higher (79F).

Are Amphipods Good For A Reef Tank?

Yes, Amphipods are good for reef tanks because they eat fish waste and leftover food in the tank, and they also prevent the growth of excess algae because they consume those as well.

Since Amphipods are quite small, they can fit themselves in the nooks and crannies of rocks and substrate. By doing so, they consume different types of unwanted algae in the tank such as hair algae, slime algae, staghorn algae, and other types of nuisance algae.

So if you want to get rid of algae in your tank and maintain a clean tank aesthetic, getting Amphipods would be the best course of action.

Are Flatworms Bad For A Reef Tank?

Flatworms aren’t necessarily bad for a reef tank since they don’t cause any harm to your tank inhabitants, however, there’s a possibility for them to irritate some corals. Also, they make the aesthetic of an aquarium look bad.

You don’t have to be worried about eliminating the flatworms in your tank because the process of getting rid of them is quite easy. First and foremost, these flatworms tend to disappear all on their own after a while.

If you don’t want to wait, there are a few options you can do to get rid of them, some of which are:

  • Vacuum the flatworms out of the tank.
  • You can make your fish eat the flatworms. Fishes like the Yellow Wrasse, Melanurus Wrasse, and Six-line Wrasse eat flatworms (take note that this is theoretical, however, some aquarists claim that their Wrasses do consume flatworms).
  • Another solution would be to get yourself a nudibranch. Nudibranchs do consume flatworms, other species of nudibranchs solely consume flatworms. Some aquarists argue that this isn’t an ethical approach in ridding an aquarium of flatworms since the nudibranch would starve once it’s eaten all the flatworms in the tank.

If you still want to go for this option, then the best thing you can do is to return the nudibranch to where you bought it once it’s done its purpose.

  • Another solution would be using a chemical product. The recommended product for ridding your tank of flatworms is the Flatworm eXit by Salifert. This product claims that it’s completely safe to use in a reef tank, however, it does indicate that it can cause harm to worms or feather dusters.

You must be cautious once you use this product. Why? Well, this product effectively kills flatworms, which is good but also bad because there’s a possibility that marine flatworms release toxins once they die. If you want to know how to do this procedure safely, click on this link.

Are Sponges Bad For A Reef Tank?

Yes, sponges are bad for a reef tank because they are toxic, they compete with corals in getting nutrients, sponges grow too much and kill corals in the process (e.g. growing inside corals), and they can clog aquarium equipment.

If you plan on getting corals for your reef tank then it’s best to avoid sponges altogether. The only instance you can have sponges in your tank is when you don’t have plans on having corals. These two organisms can’t coexist in a single reef tank, that’s a fact.

How Do I Know If I Have Dinoflagellates In A Reef Tank?

You’ll know that there are dinoflagellates in your reef tank once your tank water appears to look dirty, if tank inhabitants are starting to die, and when pH levels suddenly become low.

It’s normal to see a few dinoflagellates in a healthy tank, however, once their population increases and toxic types begin to surface in the tank, then that would be a problem already.

Dinoflagellates don’t go away on their own so long as there are ample amounts of food sources and light. The only way you can effectively remove these in your reef tank is by manually removing them using a filter sock while introducing carbon to the tank to keep the toxins at bay.

 Here are other methods in removing dinoflagellates in your reef tank:

  • Use 3% hydrogen peroxide and only use a small dose. The recommended dose would be 1mL per 10 gallons.
  • Remove all light sources from the tank. You can make use of a blackout curtain or cardboard to cover the entire tank to prevent light from entering your reef tank. Dinoflagellates need photosynthesis to survive so cutting off light would slow down their reproduction stage.

Take note that killing the lights won’t kill dinos, rather, it would only slow them down when they’re reproducing.

  • Get rid of GFO in your tank.
  • Increase nitrates and phosphates in your tank (take note that this step is a bit tricky to do since tank inhabitants will suffer from an increase of nitrates and phosphates). It’s best to transfer your tank inhabitants first before proceeding with this method.

Do I Need To Dose My Reef Tank?

Yes, you need to dose your reef tank because the intake of calcium, magnesium, and alkaline begin to increase when corals grow.

Several corals can survive with water changes, mainly these are soft corals. However, if your reef tank contains LPS and SPS corals then you’ll need to dose your tank.

Dosing or supplemental dosing is when you put Calcium, Magnesium, and Alkalinity into your tank water. The process can either be done manually or by using a liquid dosing pump.

Alkalinity is an important element for corals since they use this for the development of their hard skeletons while Magnesium helps in maintaining the calcium and alkalinity.

If you start to notice that your Calcium, Alkalinity, and Magnesium levels are starting to drop, it’s high time to add some salt to your tank. If you’re looking to get salt for your tank a recommended brand would be Instant Ocean.

According to The Beginners Reef, there are other ways to dose your tank apart from adding salt:

When Should I Add Refugium To My Reef Tank?

You should add a refugium after cycling your tank and have made nutrient levels rise. Aquarists have found this method to give great results to their reef tanks.

The most effective way in maximizing the function of your refugium is by setting it up in a sump. If you’re looking for an efficient and cheap way of installing a refugium then this would be what you’re looking for.

What makes this sort of setup great is its capability of filtering out organisms before they enter your main tank.

When it comes to maintaining your refugium it’s a pretty simple routine. All you have to do is harvest the macroalgae in your tank every two to four weeks. This frequency would vary per tank since some tanks have macroalgae that grow quicker than others and vice versa.

Can You Run A Reef Tank Without A Skimmer?

Yes, you can run a reef tank without a protein skimmer. Protein skimmers do minimal changes to a tank, in some cases, it has a bad effect since it will compete with a deep sand bed when it comes to taking up proteins.

There’s a reason why most aquarists prefer not to have a protein skimmer and this is because they already have a deep sand bed and these are home to filter feeders. Filter feeders are mostly composed of macro and microorganisms and said organisms in the tank are responsible for consuming protein and reducing nitrates.

Since the DSB already does a fantastic job at keeping protein and nitrates at bay, there’s no need to have a protein skimmer installed in the tank. By not having a protein skimmer installed in the tank it would reduce the likelihood of competition against filter feeders (the presence of protein skimmers takes away the only food source of filter feeders).

If your reef tank doesn’t have any DSB, fish, or other tank inhabitants that would consume filter feeders, then having a protein skimmer installed in the tank would provide a bit of benefit (e.g. improving water quality).

Moreover, if your reef tank doesn’t have any filter feeders, then protein skimmers would do a great job of removing protein.

Do Snails Reproduce In Reef Tanks?

Yes, snails do reproduce in reef tanks, specifically, stomatella, trochus, ceriths, columbellidae, nerites, nano conch, and collanistas are snails that can reproduce in reef tanks.

Not every type of snail can reproduce in reef tanks, for instance, nassarius snails find it hard to reproduce in reef tanks. Different types of snails have varying needs and not all reef tanks have the same reef chemistry.

The ability for snails to reproduce in reef tanks would largely depend on a reef tank’s chemistry.

Does A Reef Tank Need White Light?

No, a reef tank doesn’t need white light because they don’t get any benefits from it. Aquarists are the only ones who benefit from white light whereas corals benefit from blue light.

Having a white light installed in a reef tank isn’t mandatory since it doesn’t provide any benefits to reef tanks, especially corals. However, if you want to see your tank inhabitants better then you can choose to install white light.

Remember, it’s important to provide the appropriate light for your reef tank since this would be their source of food (this applies to corals) and it would ultimately help them grow healthier skeletons.

You can mix both white and blue light in your reef tank so long as it’s balanced. Moreover, it’s best to keep your white light’s brightness less than 50% so that the growth of the corals won’t be affected.

If you’re planning on adding red light as well, that’s also doable as this is preferred by algae. Be cautious though since there’s a possibility for an algae bloom. Another thing, be wary of other types of corals since they don’t fancy red lights (e.g. Leptoseris and Stylocoeniella).

How Long Can A Reef Tank Go Without Light?

A reef tank can last 2 to 3 days without light and the tank inhabitants would be completely fine after that blackout period.

Several aquarists agree that corals and other tank inhabitants can perfectly adapt in a completely dark environment for two to three days without anything bad happening.

However, there can be a possibility where you’ll have dying corals once you do this, but do take note that this wouldn’t be due to the two to three-day blackout.

Likely, the dying coral’s health was already deteriorating before initiating the two to three-day blackout. If that’s the case, then having a blackout won’t save your dying coral/s.

Remember, your safest bet is to not exceed the two to three days of blackout in your reef tank.

Light is an essential part of a reef tank since corals need these to grow healthily, it stimulates the pigments of corals, it provides photosynthesis to zooxanthellae, and lastly, it helps with providing an enhanced immune system to fishes and other types of invertebrates.

Best Reef Tanks

Coralife LED Biocube Aquarium, Fluval Sea Evo V Saltwater Fish Tank, and SeaClear Acrylic Aquarium are some of the best reef tanks you can get in the market (Amazon).

The following products mentioned are highly rated by aquarists and they also come with accessories already so you don’t have to go through the hassle of buying accessories in pet stores.

The best product out of the three would have to be the Fluval tank because not only does it come from a reputable brand but it’s also equipped with neat features such as:

  • Aluminum waterproof casing
  • Three-stage filtration Fluval media
  • A feed door that’s easy to access
  • A stylish honeycomb design at the rear of the aquarium

Are you interested in these reef tanks? Check below to see each one:

  • Coralife LED Biocube Aquarium
  • Fluval Sea Evo V Saltwater Fish Tank
  • SeaClear Acrylic Aquarium


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