Brown diatom algae is usually the first problem algae that a new reef aquarist encounters. A bloom of brown algae often occurs soon after one introduces new live rock to a reeftank. This bloom occurs because of the curing of the live rock introduces of silicates and nutrients. A brown film soon coats everything inside the tank. Control of brown diatom algae is relatively easy. The first thing to do is to purchase Trochus or Astraea snails that eagerly consume the brown diatom film. I personally prefer Trochus snails because they seem more robust than the Astraea strain. I've had good results purchasing Trochus snails from IPSF. There are other snails that will clean the glass such as Nerite and Strombus snails, but Trochus and Astraea snails are the brown diatom cleaner workhorses. The second thing to do is to perform regular water changes to remove any excess nutrients and silicates from the water. The third thing to do is to have an effective protein skimmer to help with the nutrient removal. The fourth thing to do is to cut down light intensity or duration. The final thing to do is to have some type of chemical filtration such as carbon or ChemiPure help with the nutrient removal. I would rank the methods above from most important to least important.
Red slime algae (cyanobacteria) usually breaks out on top of the substrate. There are two main means of control for this algae. One is increased water flow in order to decrease the stagnant areas immediately above the substrate. Two is excess nutrient control as detailed below.
Green hair algae is the real scourge of a reeftank. This algae loves the high light and current conditions of a thriving reeftank. Green hair algae can take advantage of any excess nutrients faster than most corals. Scrubbing of the hair algae is only a temporary measure. By following the steps below, I've been able to control hair algae outbreaks for over a year:
1.Make sure your protein skimmer is working correctly. A protein skimmer works 24 hours a day to remove excess waste and nutrients from a tank. If the venturi is clogged on a venturi skimmer or there is another problem with other skimmer designs, waste will not be exported from your tank and algae will take advantage of the waste. On my 20-gallon reeftank, the venturi on my CPR BakPak 2 consistently clogged so I added a limewood airstone to it in order to make sure that a large amount of air bubbles were always working to export waste.
2.Make sure your protein skimmer is large enough. There has been debate about overskimming a tank and whether one should skim a tank at all. But when a tank is new or when there are algae problems, "size" always helps. For my 50-gallon setup with a 29-gallon refugium, I purchased a CPR SR4 for the sump that is substantially larger than the CPR SR2 (basically an in sump BakPak 2). The SR4 consistently extracts gunk out of the tanks. Both hard and soft corals thrive in the 50-gallon tank and sponges grow in the tank and the sump so I don't think the SR4 overskims the tank. Some sponges and fanworms have disappeared, but I feel the SR4 helps me maintain the coral, fish and crustaceans that I'm most interested in. From what I've read, I think overskimming problems occur most often with downdraft skimmers. I've been very happy with the venturi style skimmers from CPR, but I've read good things about the needle wheel skimmers, and I may try them in a future tank. I think if a tank has been stable for over six months, the bioload is low, water changes are consistent, and there are other means of nutrient export via macroalgae and chemical means, one can experiment with decreasing or stopping skimmer use
3.Decrease lighting. I cut lighting down to five hours a day (two 55 watt Power Compact lights - 1 6700k and 1 7100 K) from eight hours a day when I had a green hair algae problem in my 20-gallon tank. Another way to decrease lighting is to put a filter or grate between the light and the tank. I've read some people even cut out all lighting for a while until they have problem algae under control.
4.Stop adding any trace elements or supplements. Algae are very opportunistic and additional trace elements or supplements will often boost growth. The major element to control is iron. If a product doesn't list its ingredients (some proprietary supplements don't list the ingredients), don't add it to the tank since you might be adding something that will greatly increase algae growth.
5.Perform regular water changes. Regular water changes will decrease the level of wastes and nutrients in the water. Water changes will also supplement the tank with trace elements that a trace element supplement may not fully supply. It's easy to become lazy and not pay attention to regular water changes. A calendar in plain view where one can mark down and see when the last water change was made is invaluable in maintaining a regular water change schedule. Everyone has different advice on how often and how much concerning water changes. I think the key is to be consistent with your water changes and observe how the organisms in your reeftank are doing. Every reeftank system is unique regarding its water change needs. I change 20 liters of water in both my 20-gallon and 50-gallon tank with 29-gallon refugium every three to five weeks. The volumes of both systems are very different, but both tanks are doing well with the same schedule of water changes.
6.Make sure makeup water is pure. Algae love the phosphates and nitrates often found in tap water. Phosphate and nitrate test kits will show if your tap water is contributing to your algae problem. If phosphate and nitrate levels are more than 0 ppm (my tap water measured out at 50 ppm nitrate), filter the water before using it as makeup freshwater or as source water for saltwater changes. I use a 50-gpd RO-DI filter from Kent Marine. Its output is about half the advertised amount. I think this may be due to water pressure and temperature factors. Wastewater from the RO-DI filter is sent to a rain barrel for use in the garden so that wastewater isn't wasted. The Kold-Steril filters look interesting because they don't generate any wastewater. If water needs aren't great, one can obtain RO water from retail filtered water companies or vending machines (which is what I did when I first started out my 20-gallon reeftank).
7.Introduce additional herbivores. As mentioned above in the brown diatom algae control section, introduce additional herbivores to control the algae in the tank. Trochus, Astraea and Nerite snails all help to control the algae film in the tank. Hermit crabs help pick out hair algae. I've been very happy with the reef cleanup crews I've purchased from IPSF and GARF.
8.Introduce additional detritivores. If excess food isn't eaten, it will decay and add to the nutrients and waste in the tank. Addition of bristle stars, bristleworms, hermit crabs, Nassarius snails and sea cucumbers will help control the excess food that a reeftank's primary fish and invertebrates don't consume. A detritivore kit from IPSF or Inland Aquatics will also help if one has a sand bed in the reeftank. A reef aquarist can decide what are the best detritivores to add to a tank. I've had success with hermit crabs in all my tanks. The bristle star in my 20-gallon tank has grown in size, but I've never seen it cause any damage to corals or fish in the tank. I purchased quite a few Nassarius snails for my tanks, but they all have disappeared. I think something preyed on them or something about the conditions of my tanks didn't agree with them. I've added small bristleworms to my 29-gallon refugium, but I hesitate to add them to my main tanks. I just don't want a bristleworm explosion. I think my Peppermint shrimp have been controlling my bristleworms and they may have also been the cause of my Nassarius snail disappearance. In my 50-gallon tank and 29-gallon refugium, I can see the trails made by the worms in the substrate.
9.Introduce macroalgae. When I set up my first reeftank with a 20-gallon aquarium, one of the first items I placed in the tank was some Caulerpa sertularoide. It survived through my introduction of substrate and uncured live rock. When the Caulerpa was in the tank, I never had any hair algae problems. Caulerpa grows quickly and since my 20-gallon tank was doing well after a few months, I pulled the Caulerpa out since I was tired of trimming its rampant growth. Soon I had a hair algae problem that lasted for months. I scrubbed hair algae from both corals and rocks. I looked back over my logs and I noticed one of the things that changed was the removal of the Caulerpa. Luckily, I was able to acquire some Caulerpa racemosa, and since I've added it to the tank, I've had no hair algae problems. I like Caulerpa racemosa or Grape Caulerpa because of its compact growth. Caulerpa grows fast and can quickly spread in a reeftank. Controlling the quick growth of Caulerpa may seem like a chore, but remember that pruning Caulerpa is a lot easier than scrubbing hair algae. In my 29-gallon refugium, I've been growing Red Gracilaria I obtained from IPSF. This macroalgae serves two purposes. It sucks up any excess nutrients in the 50-gallon tank that it shares a sump with, and it functions as a food source for the Yellow Tang in the 50-gallon tank. One note of caution with Caulerpa is that it sometimes becomes completely white and disintegrates. I've seen this happen when rampant growth of the Caulerpa racemosa isn't controlled. If regular pruning is done, the Caulerpa appears to maintain its color and high growth rates.
10. Chemical controls. Poly Filter and carbon can help remove the nutrients that nuisance algae needs. Poly Filter becomes very dark when it has removed wastes from the reeftank. This is a helpful feature to gauge the waste level of the water and when the Poly Filter needs to be changed. As a reeftank matures, I rely more on the other means of waste removal. But when a setup is new or when the nuisance algae problem is severe, chemical controls can definitely help.
11. Controlled addition of food to tank. If the tank inhabitants can handle it, feed small amounts of food every other day or even longer intervals. Make sure the food isn't messy and spreads all over the tank to decay. While I was trying to control the hair algae in my 20-gallon tank, I just fed 5 Hikari pellets every day to the two clownfish and the neon dottyback in the tank. The fish quickly ate all the pellets and there was no food going to waste in the tank. Make sure the food you're feeding is low in phosphates. I've read that frozen gel food can be high in phosphates, which contributes to algae growth.
12. Physically remove excess algae. Sometimes, the nuisance algae growth is overwhelming for the herbivores in the reeftank. This is when human hands must physically pull out and scrub the nuisance algae. The herbivores then have a chance to control any new growth. It's quite amazing how quickly the nuisance algae can grow back. One can spend hours removing nuisance algae from a tank, but a week later, the tank must be scrubbed again. But if a reef aquarist physically removes nuisance algae and follows the steps outlined above, nuisance algae outbreaks should come under control. Patience and persistence are required, but the nuisance algae scourge can be controlled if the right steps are taken.