Ah, now the picture above is the way we should feel when we view our aquariums: peaceful, relaxing, colourful and any other fitting words that can be thought of. Many aquarists do get this, including myself. Just sitting and looking, a great stress destroyer. Maintenance becomes more enjoyable, feeding the fish – well yes, everything.
Sometimes things can go wrong though for some aquarists. When the aquarium was set up and completely newly stocked all was wonderful. The aquarist felt so proud of the achievement. As time passes small anomalies are noticed, a bit of brown here, a bit of green there and these bits seem to increase in size either slowly or surprisingly quickly. Eventually the aquarist realises the problem that is developing, it’s algae and not the various types that are welcome and add to the beauty of the aquarium. It’s the yukky stuff. A very technical term but all aquarists know what it means.
Usually there is good reason why yukky green or brown hair or slime algae has appeared and a check of seawater readings will often confirm contamination. Often nitrate is present in too high an amount, or phosphate that can also cause trouble. These are the first to check and the checks are easy. Nitrate in a reef system should be 10 ppm (parts per million) or lower, in a fish only system 30 ppm or lower. Phosphate should be at best undetectable, or no more than 0.03 ppm.
If the readings are unacceptable obviously something needs to be done. First a check of newly made up saltwater (such as that prepared for a partial change) should be completed. If there is an unacceptable reading then check the fresh water supply, the salt used for the mix isn’t the culprit. If the supply is tap water this can sometimes be contaminated. If it is, then don’t use it as delivered, obtain an RO (reverse osmosis) filter. The water has to go through a membrane which is very very fine. The water leaving the filter is usually 95 to 98% pure. To protect the membrane there is usually a carbon filter first. The filters are not usually too pricey. It is worthwhile having an RO filter whatever as there are often elements in the fresh water that are not required.
If the fresh water in use is acceptable, then the problem is with the aquarium or more accurately with the aquarist. If the system has been set up with all required equipment of the correct size (protein skimmer etc) then that is not the problem. Perhaps it is over enthusiasm leading to over stocking. The desire to get life in the aquarium is very strong and tests patience with everyone. Those without any experience could have ‘one of those and one of those, oh yes let’s have one of those….’ which leads to potential incompatibilty of specimens and also aquarium overload. Overload is where the biological filter has trouble coping with the number of fish present. The formula for fish load should not be exceeded and should take into account the eventual size of the fish. The larger the fish are the less fish there should be. What is ‘overload’? It is mainly (there are other consequences of overloading) where the biological filter which performs the nitrogen cycle (ammonia/nitrite/nitrate) cannot deal with the amounts the fish are producing. This is made more serious as the fish have to be fed, as there are too many contamination by overload is made worse. A simple way to check the holding capacity of the aquarium is to allow as a maximum 1/2″ (approx. 1.5cm) of fish per gallon of seawater excluding any sump. The 1/2″ excludes the tail. Fish grow of course and it is the final size that is considered. So if a 2″ (approx. 5cm) fish grows to 4″ (approx. 10cm) then that equates to 8 gallons. Introducing livestock should be done very slowly to allow the biological filtration to adapt and cope (the biological filtration should be initially matured before livestock introduction). Particularly with a reef tank where corals that are more sensitive to seawater quality are present half the potential fish should be slowly introduced. If all is well then another could be introduced, then perhaps another after a good period of time and so on.
Ok, so nitrate is present, the aquarium is not overstocked and the seawater going in from week to week is nitrate free. The next thing is the feeding regime. Uneaten food rots down and presents even more work for the biological filter. So feed slowly, just a little at a time making sure that as much as possible is taken by the fish. How this is done varies as some fish have extra dietary requirements. Overall though fish lose their desire to get the food when more or less full but they can still look as though they will eat more by hanging around. Many also learn to look hungry by hanging around when exterior movement is detected, this is a response that is natural: ‘Any food, I want it!’ Resist this. Inexperienced aquarists can overfeed by kindness and concern for their livestock.
Two final points. The first, is the biological work performed by an exterior or interior power filter? If this is so, then the filter will convert ammonia to nitrite and nitrite to nitrate, but unlike live rock, it will stop at nitrate and release nitrate into the seawater. This is because the removal of nitrate requires an environment very low in oxygen, and of course the power filter is pumping oxygenated seawater through. So if a power filter is in use an increase in the amount of seawater routinely changed could bring the nitrate level under control.
The final point? Well, that’s about the title. Oxygen presence in seawater is lower than in freshwater and the higher the temperature the less oxygen there is (another reason not to overstock). So the seawater needs to be well oxygenated this being mainly accomplished by seawater movement and the aquarium seawater surface, plus any weirs etc. How can oxygenation have anything to do with the prevention of algae in the aquarium?
I use a hang-on protein skimmer. When originally fitting it I found that the short plate outlet from the skimmer didn’t reach the seawater surface because of the aquarium horizontal side struts. Therefore I manufactured from clear plastic a short extention plate over which the returning seawater could run back to the aquarium. There are two very low seawater retaining walls glued to each side. It has a shallow slope and measures only 4″ across by 3″ front to back (approx. 10cm x 8cm). The seawater flows fairly slowly and covers the plate to a depth of about 1/8″ (approx. 4mm). The plate is under and close to a marine white fluorescent tube, about 3″ (approx. 7.5cm) away. The plate came into use over 13 years ago.
The plate started to discolour with this and that. It is cleaned each week with a tooth brush. I noticed after a while that short, stiff and bristly algae growth had begun and this continued until all the plate under seawater was covered. The tooth brush pulled out bits of rubbish but nothing to worry about, the bristly algae remained. Then I noticed green algae coming out, not a lot but it was there and still is. This the tooth brush easily removed still leaving the bristly algae in place.
‘Oh dear’ thought I, ‘not the dreaded green filamentous algae!’ But no, nothing appeared like that in the aquarium from the start and never has for more than 13 years. There is colourful and desirable algae present in the aquarium but nothing unwanted. Relief!
Obviously the closeness of the plate to the light has helped generate the green algae and perhaps the bristly brown stuff too. Clearly there has to be some nutrients available to feed this algae. The nutrients must be low as the aquarium tests are fine. Whatever nutrients are present are being removed by the plate algae and as the nutrients are very low this can only be good.
So as an ongoing assistance to algae control a plate could be placed in an appropriate position under the lights where it is easy to get at and clean. If not a skimmer, a small pump could be used to cause seawater flow over the plate. Growths of some sort could occur which could be, likely will be of benefit to the aquarium. A thin layer of slowish flowing seawater takes up oxygen readily, so even if algae nutrients are not taken up by algae growth there is an enhancement to oxygen saturation which can’t be bad. The plate is very cheap and easy to make with plastic and silicone. It’s worth a go and can be easily removed if desired. The plate described above serves 41 gallons.
Unwanted yukky algae is a real pain and can take time and patience to remove. Getting rid of it or not getting it in the first place by careful planning and ongoing care will bring back the peace and stress reduction that most aquarists enjoy.