Diatoms in a Reef Tank

What Causes Diatoms in a Reef Tank?

If you notice a buildup of brown algae in your reef tank, there is a good chance you are experiencing a diatom bloom. While these microalgae are not considered harmful to your community, they can make your reef tank look dirty and are often an indicator of quality issues.

Diatom bloom is caused by an imbalance of compounds such as silicate, nitrite, and ammonia. Diatom algae thrive on these compounds, and they can easily overtake a tank if the food is there to sustain them.

This imbalance can have several causes, including the introduction of new substrate, decor, or water. An insufficient filtration system will allow these levels to get out of control, and they will continue to pop up until the underlying problem is dealt with.

How Do I Get Rid of Diatoms in a Reef Tank?

To get rid of diatoms in a reef tank, you need to make sure this is what you are working with and then remove any sources of food for diatoms. The long-term goal is creating an inhospitable environment, but there are also some more immediate ways to deal with a diatom presence.

These microalgae are brown, and they almost look like rust settling across every surface in your tank.

The only way to be 100 percent sure the algae are diatoms is by looking at them under a microscope. Diatoms have an unmistakable glassy appearance, but you can usually assume they are diatoms if they feel gritty between your fingers.

Your main focus when getting rid of diatoms in a reef tank is removing anything they might eat. Diatoms thrive on nitrates, phosphates, and silicates. The most common sources of these materials are new substrates (usually sand) or improperly treated water, like RO water or tap water.

Make sure your equipment is functioning properly, so it can clean out waste from the water, reducing the available food for the diatoms. You can remove the algae from the glass using an algae scraper. Take your time, working from bottom to top, and dispose of the diatoms you displace.

Use a gravel vacuum over the substrate to remove loose diatoms on the floor of the aquarium, but take care to not bury them. You can reduce suction by pinching the tube. You should also mix up the substrate a bit, so you can vacuum anything hiding beneath the surface.

Decor should be removed from the reef tank and scrubbed clear of diatoms before reintroduction. You can use chemicals to facilitate cleaning, but make sure everything is thoroughly rinsed before putting it back.

Additives like Vibrant and Phosguard can assist in depleting the food source of diatoms. You can also increase the flow of water to make it difficult for them to breed, and use a UV sterilizer to eliminate their ability to reproduce.

Do Diatoms Mean My Tank is Cycled?

While diatom bloom usually occurs after a tank finished cycling, it is not a key indicator that a reef tank has completely cycled. The only thing that diatom presence indicates is that there are enough nitrates, phosphates, and silicates to sustain a diatom presence in the tank.

Cycling involves establishing the nitrogen cycle in your reef tank to ensure the comfort and health of any tank inhabitants. There are several methods for cycling a reef tank, and many choose to use bacteria from a bottle for the fastest results.

You will know your reef tank is cycled when you have established a complete nitrogen cycle. This involves testing the water and coming back with no readings for ammonia and nitrite and rising levels of nitrate.

What Will Eat Diatoms in a Reef Tank?

There are several types of snails that will eat diatoms in a reef tank, including:

Nerite snails eat both black and brown algae, and they are considered the most efficient variety to combat microalgae presence in a reef tank. They live longer, tend to be slower, and do not leave a film on the glass.

Cerith snails will eat diatoms in a reef tank, and they stay toward the bottom of the tank. They are more active at night, and they will also eat uneaten fish food and other waste that feed diatoms.

Trochus snails will eat diatoms as well, but they focus more on the rocks, decor, and glass of aquariums. They are not likely to dive into the sand and pursue any diatoms waiting in the substrate.

Tiger conches are great for oxygenating any dead spots in your tank and preventing the growth of certain algae. They are also great for eating diatoms buried in the sand beds that other snail varieties may overlook.

How Long Do Diatoms Last in a Reef Tank?

Diatoms usually only last 2 weeks to a month in a reef tank. At this point, silicates should be depleted. The diatoms will start to fade in color, and they will not be able to reproduce or sustain a presence.

This is a great point to go through and make sure your reef tank is not hospitable to diatoms. Unless you address the root of the problem, you will find diatoms continuing to repeatedly bloom.

Conditions that can make diatoms last longer in a reef tank include:

  • Overfeeding fish
  • Using improperly treated water
  • Insufficient filtration
  • Irregular water changes

To limit the length of time that they last and prevent a return, make sure waste in the tank is kept to a minimum. Do not overfeed your fish, and make sure your filter is in good working condition. Adding a protein skimmer will help in preventing waste buildup, and weekly 20 percent water changes should be sufficient.

Any water added to the tank should be properly treated and free of silicates to reduce the time diatoms spend in your reef tank. Make sure your RO/DI system is not faulty, and change the DI resin as needed. You can use a silicate test to determine whether your system is working properly to remove silicates.

As long as you handle the underlying issue, diatoms should not last longer than a month in a reef tank, and they should not come back.