Looks like you're ready to start up! If you're using all Live rock and not base rock you can add fish as soon as your diatoms start to die back.
Diatom blooms / Diatom blossoms
I wanted to share a brief description of diatom blooms, what they are, how they behave, and how to dispose of them. Anyone that is new to this hobby, or anyone starting a new tank, is much more likely to experience diatom blooms, but it can happen to any tank at any time. It’s far more common in new tanks where the water has not fully cycled. This is an important reason to always let water cycle in a new tank before adding any livestock. To be proactive, and potentially avoid diatoms and other problems altogether, I recommend a one month cycle. A one month cycle allows for new water, salt, sand, rock and other chemicals to settle, plus time for two water changes. I recommend a 25% water change every two weeks. This can depend on many factors, like your bioload, what you have in the tank, and the quality of your water, sand, and rock. But as a general rule, two week changes will be healthier than one week changes. Okay, back to the main point. What are diatoms?
To start, diatoms are a member of the Kingdom Protista, which includes more than 20,000 different species of algae. Diatoms are in a class called Bacillariophyceaea. (Remember Life Science classes in junior high? (Kingdom, Phylum, Class, Order, Family, Genus, Species). So, not all diatoms are the same, but most are similar, in the same way that most humans are the same, compared to horses or plants.
Construction and Use
What makes a diatom? One of the main characteristics of a diatom is that they have an outer shell, made of silica. Silica by itself, is not good or bad. It can be both. But as with all things, moderation is the key. Think about your own body. Your body needs sugar. So, you may opt to consume soft drinks. Your body doesn’t need soft drinks, and they are mostly bad for you. But, they do contain mostly water, which your body does need. Too much sugar can lead to diabetes and feed cancer cells. But not enough causes problems too. Silica is no different. Silicates in small doses in a tank can be beneficial, but too much is definitely a bad thing. Too many silicates often lead to diatom blooms.
What does a diatom bloom look like?
If you check your tank one day, and discover a rust color or redish brown algae growing on your live rock, or if your “white” sand now seems to have a rust stain (brown or red rust), it sounds like you have a diatom bloom! So, if you are new to the hobby, and see this for the first time, it’s natural to panic. What’s going on? What is that stuff? Is it bad? What’s wrong with my water? After talking to your local fish store, pet store, readying some online forums, and showing some pictures, people will say, “Oh. It’s just a diatom bloom. Just wait it out for a week or two, and it will go away on its own.” While they will be correct most of the time, their reason for being correct is probably not correct (not that it matters). Just keep to your schedule. Sure, diatoms look scary, and they decrease the available oxygen in the water, but most of the time, they are harmless. It is only in rare occasions that they actually cause a problem. So, the best course of action to “control” diatom blooms is sometimes… do nothing. Keep to your schedule of water changes.
Out of Control
In rare occasions, diatoms can get out of control, reproduce quickly, and actually form a “crusting” layer on your live rock or sand, which essentially closes off the pores that live rock need to filter beneficial bacteria and algae. Crusting on sand or coral can have the same effect. Anything that is porous in a tank is meant to be porous. So, having a crust that closes off those pores is bad. Always bad. Closing off the pores means that the coral will suffocate, live rock and live sand won’t be able to filter properly, and bad things start happening.
I don’t have any scientific studies or proven statistics that I can show, but my guess would be that 99 times out of a 100, diatoms don’t cause a problem. They are just ugly looking in the tank. They often can’t keep reproducing successfully, and simply run out of gas, so to speak. Think about pushing a car down a hill. It will gain speed. But eventually, it will stop. Hills and mountains don’t go downhill forever. So, the car either crashes, hits something, or levels out and loses momentum. Diatoms are the same way. The reproduce and grow rapidly. But, in order to reproduce, they have to split. As they reproduce, they get smaller and smaller. With every reproduction, they grow weaker and weaker.
And, as they break down, this nuisance diatom actually turns into beneficial bacteria. They become a source of food for your “filter feeding” livestock. Crabs, snails, and shrimp will eat it. Secondly, diatoms consume nitrates and phosphates, which is also a good thing. You don’t want nitrates or phosphate in your water at all, ever. If you are new to this hobby, you should know that nitrates and phosphates in your water are also bad. So, if you have a phosphate or nitrate problem, diatoms may be the cure in disguise. Also, if you have a Protein Skimmer (highly recommended in a reef tank), the protein skimmer will help to eat phosphates, nitrates, and diatoms. A protein skimmer, especially for a reef tank, is a great weapon to remove bad stuff from the water, without affecting the good stuff. (Stuff is a very scientific word here that I won’t attempt to explain further).
How did the diatoms get in my tank? Where did they come from?
The answer is simple. You put them there! If you are starting a new tank, you put the sand, water, rock, and other media in the tank. When you put all of that stuff in the tank, you put the diatom in there. The same is true for mature tanks. Maybe your tank has been running for years, then one day you notice a diatom bloom. How did that happen? This is a little bit harder, but think about what you have put in the tank or changed in the past one, two, or three weeks. New fish, new rock, new coral? Did you vacuum the sand and stir it up? Did your water source change? Did you switch from tap water, to RO water, RODI water, or purchase your water? Did you change salts or additives?
On the one hand, the diatoms are directly your fault, because you put them there, even if you didn’t know you put them there. But at the same time, it’s tough to take responsibility for something that you didn’t even know you did in the first place, right? So, don’t beat yourself up. It wasn’t intentional. In fact, you weren’t even aware of what you were doing. And, this is a problem that takes care of itself over a period of a week or two, most of the time.
Why Are They Appearing?
Some people assume that diatoms appear in their tank because they did something wrong. It’s not necessarily true. Simply put, diatoms formed in your tank because your tank has too many silicates. Silicates are more prevalent in sand, especially since everything in a tank settles to the bottom. That is most likely where they came from. But, silicates are also found in live rock, and in your saltwater. If you are using tap water for water changes, it is also likely that your water source has too many silicates. If this is the case, you may have a more serious problem. You may need to change your water source and wash or change your sand. Also, as mentioned above, using a Protein Skimmer in combination with RO water and live sand and live rock will help a great deal. If the water that you use to top off and use for water changes has silicates in it, then the population of diatoms will have an unlimited and bountiful food source and may not stabilize. Even when using reverse osmosis and deionization, the filtered water may contain silicates. It doesn’t take very long for the silicates in your tap water to clog the membrane and allow more silicates through. So if you get a diatom bloom in a mature tank or if your diatom bloom does not go away, then you will need to check (or change) your source water and water filters. I should also mention that certain types of sand that are not made for aquariums can have very high levels of silicates and silicic acid which will cause a never ending diatom bloom. These sands should be avoided unless you are sure that they are aquarium safe.
How Do I Get Rid of Them?
Now that you know how diatoms form and how the problem started, the next logical question is, “How do I get rid of them?” You may have figured this out already. The answer is, remove the silica from your water. How do you do that? Water changes, protein skimmer, live sand, live rock, and of course, time. As stated above, most of the time, the problem resolves itself. I don’t like that answer, although it isn’t wrong. Diatoms feed on silicates. So, if you are doing water changes, you should be removing silicates from the water, unless your water source is the problem. In that case, you are just feeding the diatoms. Not a good idea.
Cleanup Crew
If you have a good cleanup crew, they will also help in getting rid of the diatoms. Nassarius snails, Trochus snails, Cerith snails, Astrea snails, or catfish will eat diatoms. Personally, I prefer Trochus and nassarius snails. Trochus snails will grow with their shell, look cool, and are great at cleaning the glass and rockwork. Nassarius snails will help in the sandbed. You need both. You can have one of each in your tank per gallon. For example, if you have a 50 gallon tank, you can start with 25 Trochus and 25 Nassarius. As you add livestock (fish and coral), you could have up to 50 Trochus and 50 Nassarius in a 50 gallon. The more fish you have, the more cleanup crew you need, in my opinion, but a 1:1 ratio of each compared to your gallons should be fine. If you have mostly coral, and only one or two fish, you don’t need as many snails. Just my opinion. And, with water changes, silicates should decrease. There is an old saying in this hobby, “Dilution is the best solution to pollution.” You can also purchase diatom filter pads. They will help to absorb silicates, but I still think they are a waste of money. Lastly, the other reason a cleanup crew is important is because silicates decrease the available oxygen in the water. So, another way to help keep the water healthy in a FOWLER tank is wish an airstone. (FOWLER is Fish Only With Live Rock). I would strongly advise AGAINST an airstone in a Reef Tank. Too much oxygen in a reef tank is a BAD thing. If you have any coral at all, I would not use an airstone. But for a fish only tank, airstones are good, especially if you have diatoms. When diatoms die, they can remove oxygen from the water and become food for other nuisance algae and bacteria.
How Do They Reproduce?
Diatoms reproduce asexually at first, then sexually when they run out of silicates to feed on and/or when they get too small. Diatoms are round / circular, and they have two halves. The two discs reproduce asexually by dividing. Each half forms a smaller diatom. That is why they are called diatoms. “Diatom” is a two part word – “di” (meaning divided by two) and “atom.” Thus, an atom divided by two. When they split, they are half the size as the original diatom. Each time they reproduce, they get smaller and smaller, although there are twice as many of them. When they get too small, the diatom will produce either sperm or eggs and release them back into the water. This is a survival instinct. If there are enough nutrients in your tank, it only takes a few days for the diatom bloom to show up everywhere in the tank. If you look at your take a picture of your tank before you leave for work, and take another picture when you come home, you may notice a difference in their growth. More “rust” colored stains on your white sand and white rock. And, when diatoms start to produce sexually (sperm and egg), it’s like a baby, so it grows the same size or bigger than the parent. Again, if there are enough nutrients in the water, the diatoms may flourish. Now you have two problems. The diatoms are reproducing by splitting, then reproducing again with sperm and egg and growing. This is another reason why water changes and protein skimmers are vital.
What happens when Diatoms die?
Based on what I have stated above, you know that diatoms can decrease the oxygen supply in the water. Get an airstone if you have a FOWLR tank. If there is still an ample silicate supply in your water, those diatoms are there to stay. But, if you are doing things correctly, you are doing water changes, and you have a protein skimmer, the diatoms should start dying. When this happens, the diatoms turn into endospores. Endospores are basically an inactive organism. Diatoms form endospores when there are not enough available nutrients or when conditions are not favorable for them. When the conditions do become favorable, they can spring back to life and reproduce astronomically. This is one of the reasons diatoms may occur in a mature tank that has been running for years. You’ve done a great job of keeping your silicates low for years. Then, one day, the level rises, and those endospores turn into diatoms.
Conclusion
Okay. I know this was a long article, but you should now almost be an expert on diatoms. You know what they look like, how they form, what keeps them alive, what kills them, and how to remove them. With all of this information, it doesn’t guarantee that you won’t ever have them. But, at least you know what to do now. Water changes, a good cleanup crew, and a protein skimmers are great tools. Time is your best friend or worst enemy in a saltwater aquarium.
I hope you found this article helpful. It has taken me a LONG time to write all of this. Please comment or share your story below. It may help others learn! Also, if you are a member of other forums, please feel free to re-post this and share the knowledge. Print it out and give it to your local pet store, fish store, aquarium, etc. Have fun! It's a great hobby!
