Bob replies...

Hi Sean,

Algae is like death and taxes, you're not going to avoid them! There's not a system that will always be totally algae free (nor would you want it that way), but the difference between a somewhat algae free system and one that is overgrown can many times be traced back to how the system is started, then maintained. Begin a system with more nutrients than there are bacteria to utilize them and algae get a foothold. This would be a system that used dead sand and uncured live rock to begin. Nutrients coming from the rock have to go somewhere if there aren't any bacteria to properly utilize them! They coat the rock and sand, mainly as calcium phosphate and also accumulate in the sand and bulk water as nitrogen products, such as nitrate and ammonium. Then, add to that a hobbyist who doesn't understand the carbonate buffering system (alkalinity) and improperly uses calcium and buffer additives and the problem worsens - more calcium phosphate coating the sand and rock. And once algae become recognizable (cyanobacteria growths like hair algae and slime mats), they begin to make their own nutrients directly under their mat. They then become independent of any nutrients floating around in the bulk water. You could easily at that time have zero nitrate and phosphate and still have copious amounts of unwanted algae and/or cyanobacteria. The damage has been done! Then add the possibility of excessive bioload (too many fishes and food for the existing microbes and/or the efficiency of those existing microbes), and the problem becomes even more frustrating!

The ideal start of course is to establish a live and functional sandbed before placing too much rock in the system. And use well cured live rock when doing it. Then, a month after the bed has been established, finish the rockwork, preferable with cured branching rock. And leave much of the sandbed surfaces open for maintenance by not piling the rock like a brick wall or pyramid! Use a quality skimmer and calcium reactor and understand what it takes to maintain good water quality.

This is all easy to say, but doesn't answer your questions. However, it's necessary to point out because too many people want pieces of the ocean in their living rooms overnight! I don't know how your system was begun, but the following are some possibilities that you may want to consider.

I know of 'many' periodical outbreaks of algae that are caused by local water company's. They occasionally use a poly-phosphate additive to control rust throughout their distribution system. Legally they can do that without telling people, but if your not using a quality RO/DI unit it will show up as an algae bloom in your aquarium.

As for using any type chemical for killing a cyanobacteria outbreak, that's an incorrect approach. It will return, only now more antibiotic resistant! Cyanobacteria is useful bacteria, and one of the oldest forms of bacteria on this earth. It's the first to show itself when conditions may be getting out of hand nutrient-wise. It tells us that something is happening and possibly needs our attention. Small outbreaks of this bacterium (film-like growths) should never be seen as a problem, however, once it begins forming large 'mat-like' areas it should be siphoned out with small diameter tubing. Then some thought to system maintenance is in order, e.g., improve lighting as this bacteria prefers the red spectrum, and increase water movement in the area where its forming.

As for jumping into a system already experiencing serious algae problems, curing the problem now becomes more difficult than if the system had begun correctly. Rock is usually coated with phosphate, providing the energy to start the alga spores. Water quality may not be what it should be because the user does not know how to properly maintain it. The sandbed may be mostly anaerobic, such as with deep beds directly on the aquarium bottom, which shunts efficient microbial growth/energy usage.

I'm familiar with the brand aquarium mentioned in your letter, however, not sure if your model plenum covers the entire tank bottom or is short of the side panels by about four inches as some have been. If so, the 4 x 6 inch surrounding volume of sand is microbially inefficient when compared to the bed over the plenum. If I were to subtract that non-efficient bed volume and also subtract any plenum bed surface area covered by rock, could be most of the sandbed is inefficient. If this is the case, efficient denitrification will not happen in the covered areas and in those surrounding deep areas. Efficient denitrification is where nitrate is reduced to nitrogen gas, such as in areas that contain some oxygen (anoxic). Those areas that are oxygen free, such as anaerobic areas, only reduce nitrate to ammonium, not nitrogen gas, and ammonium is the prime algae nutrient! Unfortunately this ammonium exists in very small undetectable levels on our test kits, but enough to assist in the growth of algae.

When it comes to bed depth over the plenum grid, the recommendation of about four inches of a material with a grain size of 2 - 4 mm still applies. If the bed is much deeper, the penetration of oxygen via diffusion is hampered, thereby reducing the level of very efficient nitrate reduction. If the bed is too shallow, there's simply a reduction, volume wise, of the more efficient anoxic area. And that additional area could be considered a 'safety-net' where occasional influxes of excessive nutrients are processed, preventing any swings in overall system balance.

To help minimize such an existing condition, the nutrients that eventually breakdown to nitrate and ammonium, the proteins, should be removed with a very efficient skimmer. There are quite a few very good skimmers on the market, and have recommended some brand/models in my return letter.

When it comes to ridding the system of phosphate, nothing that I know of is better than the 'iron' based products on the market. There are three iron-impregnated pads on the market, one iron-based granular product from a US based firm, and one now being imported from the UK that I know of. They are all 'excellent' at removing phosphate. I would not recommend operating a system without one of these products in use.

Removing growths of unwanted algae by hand is necessary once it becomes visible. Depending upon herbivores once it gets unsightly is often a mistake. They only redistribute the nutrients, which mostly come back in the near future as nitrogen accumulation/algae growth. The best approach is after a major cleaning, introduce 'some' herbivores so as to help keep algae growth minimized.

You mention a sand shifting starfish, which I believe, is Archaster typicus (Thought to come from Fiji, about 4 inches across and a light tan color.) I tried one in a 125 gallon system and it was a major mistake in my opinion. It wiped out all my valuable benthic organisms! Properly constructed beds have both diffusion and bioturbation processes. Therefore the beds limited infauna, which activates the bioturbation processes, have great value. Using these benthic creatures as a food source for this starfish does not make sense! I recommend removing them.

Water movement depends upon what is being kept in the system. There is also some confusion on that subject, as volume-wise movement is different than how much actually flows by certain animals. Some stony corals need high flows, such as three to five times system volume past their bodies. Some deeper water or soft corals do well on one to three times system volume. That's why wavemakers with various on/off periods and outflows in varying directions is best in more complex reef systems. My 180 gallon system experienced temporary surges up to 2000 gallons per hour. Yet that did not occur throughout every part of the tank. Depending on its aquascaping, some portions of that tank received little flow, however, what was in those areas like it that way. The thing to do is insure all areas of the tank receive some flow, as cyanobacteria prefer stagnate areas.

Lighting is another area that needs some forethought when it comes to algae. Corals prefer the blue-green portion of the spectrum and algae prefer the longer wavelength, the red band. Metal Halides often need replacement after 12 months of use. The shift of spectrum usually begins after three months of use, and sometimes becomes visible to the human eye after six months of use. Once near twelve months, there's often a sufficient spectrum shift towards red, which provides a more viable environment for algae. Add to this the fact that when the light waves travel through bulk water that contains excessive nutrients and/or an excessive amounts of calcium ions, the light wave is further lengthened. So, in an aquarium where the bulk water contains high nitrate and calcium exceeds that of natural seawater levels, the best and newest lamps are still producing a favorable spectrum for algae! My rule of thumb is about 2 - 3 watts per gallon for soft corals, 4 - 6 for a combination of soft and stony, and about 8 watts for fringing reef sps corals.

All in all, a quality protein skimmer and calcium reactor are two great tools for helping to maintain water quality. But the overall picture of a successful system is much larger than some helpful equipment. It's really a combination of many things, and understanding microbial processes is at the root level. Then add helpful equipment and combine that with sensible bio-loads, and the result then takes on the appearance of something we had hoped for when beginning the system.

Hope this helps,

Bob