What are silicates?
Silica is a chemical that nobody wants in their reef tank. Have you ever seen a reef tank where the glass, sand, rocks were covered in a brown powdery form of algae? Normally this algae will begin to cover in patches and quickly spread to cover everything in your tank. It is not something that forms in large sheets and is fairly easy to remove.
In the beginning stages of a new saltwater tank, you will start to notice brown diatom algae. This is completely normal and as your tank cycles, the diatoms will begin to disappear over the period of a few weeks. In order for diatoms to grow and take over, it needs silicate (silicon dioxide) in the water. Silicate basically feeds the diatoms causing it to grow and spread.
Also if you are using tap water in your tank that has silicate, this will fuel the diatoms causing them to reproduce. RODI water is highly recommended.
Where do silicates come from?
There are 2 main sources of silicates in your tank.
- Tap water
- Substrate (Silica sand)
It is possible that silicates are introduced to your tank from salt as well, but the main sources are tap water and substrate. As mentioned, diatoms are normal in a new saltwater tank and are easy to remove. Most likely they will go away on their own, but there are a few other ways you can remove them as they can be an eyesore and turn into a big problem if they completely overrun your tank.
There are 4 main ways to remove silicates from your saltwater aquarium.
- Water changes with RODI
- Proper maintenance – manual removal
- Protein skimmer
- Phospate removal
When removing these silicates, it’s important to note that not only is removal important, but you need to eliminate the source that’s causing them in the first place. Most likely if you are seeing the brown diatoms growing, caused by high silicates, you need to eliminate tap water and ensure your substrate is clean and rinsed prior to going in the tank. Removing substrate down the road after your tank is cycled and maturing can be a huge job and cause problems. It’s best to avoid this issue from the beginning. Make sure you are using a quality substrate that is clean and rinsed first.
Water changes with RODI is going to be the most effective way to remove silicates. As mentioned, RODI water with 0 TDS should be used. Many people will argue that tap water can be used safely, but I disagree. If you are using tap water for a saltwater aquarium, you will most likely encounter high silicate levels and have brown diatom algae issues. Maintaining a proper water change schedule will be important, and if you do have high levels of silicates, larger water changes may be required.
Proper maintenance and manual removal is another option you can use to remove brown diatom algae. If your tank is new, you will most likely encounter this. You can use an algae pad or scrubber like the Flipper which is great for removing all forms of algae from your glass or acrylic tank. It’s good to clean your glass prior to a water change as you can manually remove algae from the water column. Keeping your substrate clean and avoiding waste and detritus build-up will also help. Read my review of the Flipper algae scrapper here.
Using a protein skimmer on your tank can also be effective for removing silicates. A protein skimmer is a type of mechanical filter that removes organic compounds from your aquarium water. Things like waste, uneaten foods, toxins, and bacteria are all things that a protein skimmer helps remove. Protein skimmers are essential as they remove organic waste before they have a chance to break down and release nitrogen compounds. An advantage of using a protein skimmer is that it helps keep your water free of toxins and is a huge support to your filter system in keeping the tank clean. They also help increase oxygen levels and overall water quality.
Removing Phosphates is also key in helping to reduce silicates. Phosphate levels in a saltwater aquarium need to be maintained at a low level. There are a few ways you can do this like protein skimming, using a media reactor with GFO, having a refugium with macroalgae, water changes, and using commercially available products like Kalkwasser, Phosguard, phosphate removing sponges and pads, Nopox.
Let’s address the elephant in the room right now. Carbon does not help remove phosphates! Actually it can be counter-productive and some carbons can leach phosphate into the tank. The best quality carbon on the market will not remove phosphates.
How and why to remove brown diatoms?
If you are dealing with high silicate levels, and the resulting brown diatom algae forms, you will want to have it removed especially if it is getting out of control and taking over your tank. Here is how and why.
As mentioned earlier, this form of algae is fairly easy to remove by using an algae pad, brush or scrubber. If you notice it forming on the rocks, you can use a turkey baster to blast it off. Manual removal is your best option. You can also choose to use members of a cleanup crew like snails that are great for eating up the algae. I mentioned in the article 13 Common mistakes made in the saltwater hobby, that rushing a new tank is a bad idea and adding livestock too soon is the wrong thing to do. So as your tank cycles and you notice the diatoms forming, this would be a good time to add your invertebrates to help with that.
There a few reasons why you should choose to remove these diatoms if they are getting out of control. When diatoms die off, they can actually deplete the oxygen levels in the water column. They can also cover corals and rock causing them to smother and die. As diatoms decompose they can actually release silicate back into the water which we are trying to remove in the first place.
For the most part, the brown diatom algae is not something to worry about. It’s when things get out of control and they begin to take over your tank you should be concerned.
Keeping silicates in check begins with the source and addressing them from the start. Using RODI water is key and adhering to proper maintenance and water change routines will be a huge help.
Thanks for reading!
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