A Question About Algae

Algae could be the aquarist’s friend and at the same time an enemy, it all depends on what type it is. A question arose recently about algae and my immediate reaction was ‘Oh no, not again, algae!’’ In fact it wasn’t so bad.

The question came from a beginner aquarist who openly admitted that she didn’t have much experience. In fact, she had done precisely four routine seawater changes with her new aquarium. The aquarium, a fish only, was not overstocked, if anything it was understocked. She was a little fed up; the excitement of actually seeing some life in the aquarium after all the patient waiting when the system was being put together was being spoilt by the dreaded algae. I was unable to see the aquarium.

Basically she had done seawater changes and after each one she advised ‘red’ algae had gone bananas. That’s what she said; I don’t think it could have been quite as bad as that!

Many aquarists have problems with various types of algae, particularly when inexperienced and when the aquarium is in its early days. I was surprised that it was red algae causing the trouble. Usually it is green hair algae, or so-called slime algae or smear algae (a thin sheet that slowly covers rocks, sand etc). Slime algae can be ‘reddish’, very dark and appear red nearly black. Another type is diatoms that are usually more golden brown in colour.

Red algae can be calcareous and branching or encrusting, or have flexible ‘leaves’. These algae types are often sort after by aquarists as they are decorative. In the red algae family there are over 4000 types. The algae though had been identified as a problem and not decorative so it cleared these types away. So the algae in question had to be a problem type, but what? Green hair algae was obviously not the answer.

When an aquarium is first started up diatoms often appear. They could cover rocks, sand etc. The diatoms rely on silicates in the seawater – if the silicates go so do the diatoms. If they appear then die back, the silicates are used up. If they then re-appear at a routine seawater change, then more silicates have been introduced. The fresh water source could be suspect. Dry sea salt does not usually cause this type of problem.

Smear or slime algae is a bigger problem. It can be quite difficult to erase but this can be achieved. The presence of smear algae suggests excess nutrients in the seawater, even in a new aquarium. Also smear algae does not like strong currents – it often tends to appear in quiet areas of the aquarium, though just to be helpful it can appear in more turbulent areas.

10% of the net system gallonage is the guideline amount for routine seawater changes, until the actual needs of a particular aquarium are known. The changes being done were of this amount.

Possibilities would have to be narrowed down, so the first suggestion was that seawater tests should be done, that is, nitrate and phosphate. A request was made to test both the seawater in the aquarium and the new seawater made up for a routine change. Ideally, in the aquarium nitrate should be as low as 10ppm (parts per million) or less particularly for a reef aquarium, a fish only could be higher but should still have nitrate minimized. Phosphate should not be detected at all hopefully, but at least the level should not be more than 0.03ppm. If it is higher, say 0.10ppm, it is too high. In newly made up seawater there shouldn’t really be any presence of nitrate or phosphate. Nitrate and phosphate are known problem algae nutrients, thus the need for control.

It turned out that nitrate and phosphate were present and ‘a little too high’, levels were not given. The seawater destined for the routine change was also tested – the same for nitrate. Now then!

So on to the next possibility. This follows the clues given – the algae become more apparent after a routine seawater change and nitrate was present in the new seawater. A check was suggested of the freshwater being used.

The information arrived that the nitrate level in the freshwater was ‘high’. Maybe this was tap water, the most likely, or it could be local spring or well water, I don’t know. Nor was the actual level given. However, ‘high’ in this instance meant ‘too much’ and this seemed to be the problem that needed to be dealt with.

Tap water is not necessarily as pure as might be thought. In agricultural areas there could be excessive nitrate levels. There could also be heavy metals, pesticides, phosphate, chlorine, chloramines and so on. The water is made safe for human consumption; there are regulations as to how much of what is permitted.

The suggestion was made that fresh water should no longer be used from that source, and that a reverse osmosis (RO) unit should be obtained. The RO unit is a membrane that only permits pure water to pass, or nearly so. The purity is usually about 95 to 98%. It is important to have a unit that incorporates a carbon filter at the front end; this protects the membrane as chlorine is removed. Chlorine could damage the membrane. A sediment filter is often incorporated before the membrane as well. RO units come in various ‘gallons per day’ sizes, one needs to be picked that is suitable for the size of the routine seawater change. RO units are very reliable and only require the carbon filter etc changing from time to time in accordance with the manufacturer’s directions. They are not particularly expensive either.

It is worth using high quality fresh water obviously for the welfare of the livestock; also dry sea salt is not cheap. Dry sea salt manufacturers produce salt that is free of nitrate and phosphate – why spoil this with poor fresh water?

Much later on it was learned that an RO unit was in use and though nothing had happened for a while, in time the algae (‘slime’ I assume) started to reduce and the aquarium became clear of it.

This seems a good demonstration that the aquarium will reflect what it receives. Feed in algae nutrients and algae could appear. In this case all turned out well.

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