Reef Ramblings

Algae.

or

The good, the bad, and the ugly!

Macro-algae.

Macro-algae are the plants that we refer to as seaweeds. They’re slightly different to terrestrial plants in as much as they don’t’ have specialist root structures for feeding, rather holdfasts, with the entire plant capable of feeding and photosynthesising. There are many species of macro-algae; they are classified as red, brown, and green algae. They can be decorative in the reef aquarium and by occasional harvesting can be used for nutrient removal. Macro-algae in the reef aquarium generally end up being one of the many species of Caulerpa, these should be utilised with care, as some species are extremely invasive, capable of taking over the entire tank and starving corals of light. Halimeda sp. are fairly safe, these are calcareous and seldom cause any problems. Sargassum sp. sometimes arrive on live rock, these tend to grow prodigiously for a time before dieing off, presumably having exhausted a necessary nutrient, possibly iodine. So again do your research.

In the reef aquarium algae are inevitable. Although, as my subtitle suggests, not all algae are bad.

The Good.

Algae are a very important part of the coral reef. They may not always be apparent but they are always present. All our photosynthetic corals contain algae known as zooxanthellae. Many of the animals we want to keep in our aquaria are herbivores, which would benefit from natural growths of algae. A couple of useful methods of maintaining reef tanks rely on the growth of macro-algae such as Caulerpa sp. for removing excess nutrients from the system.

The Bad.

When it comes down to it there are no really “bad” species of algae, they can nearly all have some redeeming feature or use. What we really mean is inappropriate species of algae, species we don’t want growing in our reefs, out competing our expensive corals for space! These are the “pest” or hair algae that often grow out of control leading people to give up the hobby. I hope that by following the methods I’ve lain out in this book that you won’t have too much in the way of problems.

The existence of algae in the captive reef is inevitable unless attention is paid to maintaining low levels of nitrate and phosphate, these two compounds can be considered as fertilisers for pest algae. Nitrate accumulates in the reef aquarium if the nitrogen cycle isn’t being successfully completed whilst phosphate accumulates as a result of the food introduced into the aquarium. If nitrate and phosphate are not kept under control it can have the effect of producing a seemingly endless, uncontrollable growth of algae that can threaten any sessile invertebrates with death by overgrowing them and depriving them of light.

Note: – Caulerpa sp. can easily cross over from being “good” to being “bad”. Some species should be kept out of the reef as they can become far to invasive, over grow corals, and be difficult to eradicate.

The Ugly.

These are the species such as diatoms, which do little or no harm to the rest of the animals in your reef but make your tank look unsightly

Algal Succession.

All new reef aquaria will go through a succession of different algae over the first few months of their existence. It’s not possible for me to predict exactly which algae are going to appear and when for any given reef, all captive reefs are unique in their make up. (You’ll find it very difficult to exactly replicate another reef unless you purchase exactly the same rock and exactly the same corals from the same shipments; even then they will not be identical due to the different animals and plants brought in as hitchhikers which will influence the reef in many differing ways.) Most likely you’ll initially encounter a brown dusting on the glass, rocks, and sand – brown diatoms; followed by blue-green algae or cyanobacteria, this will take the form of a brown, green, or red film and is often referred to as slime algae; after this you may have filamentous or hair algae to look forward to (!); finally you’ll be relieved to get to the stage where calcareous or pink coralline algae appear. To some extent these stages will overlap. It is quite likely that were you to set your tank up as far as the introduction of live rock and to then just leave it there – not adding animals of any kind – that your tank would go through all of the above stages of algal growth, one succeeding the other with no intervention on your behalf. Unfortunately this would take a long time, to most people your tank would look a right mess, and there would be no life forms of any size to hold an observers interest. Any significant other is probably going to start wondering what you’re playing at, having this expensive eyesore in their favourite room! This is why I put the emphasis on adding invertebrate herbivores form very early on.

Tim Hayes

Midland Reefs

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