<< ARTICLES :: ALGAE PROBLEMS AND HOW TO DEAL WITH THEM

Ninety per cent of my postbag on aquatic plant problems are to do with algae - green, black, brown, hairy, filament, rush etc. The plague is every fishkeeper's nightmare. From reading my correspondence, there is a common thread to cause algae. This is that algae thrives when there is poor water quality rich in nitrates and phosphates. You could be adding Baby Bio without even knowing it !

Understanding why nitrates and phosphates build up in your tank will give you a clue as to the solution. Unfortunately, if you were to test your tap water, you might be shocked to realise that in some districts it has 40 parts per million so you are off to a bad start. If you want to grow plants successfully, you have to think carefully about your filtration. This is often the prime cause of the problem. So often my letters start with details of the filtration - usually there are one, if not two, external filters combined with an internal filter. They use spray bars and air stones etc. The tanks are massively over filtrated. A 300% turnover is far too excessive. A 600 litre per hour turnover on a 200 litre tank would give you 300% turnover. Water is normally extremely clear, there is no decaying matter. Unfortunately, because of this, there are very few water changes. There is also high light intensity and high stocking level - all the classic conditions for algae growth. The high flow rate and increased oxygen not only oxidises the nutrients but converts the ammonia to nitrate which, without adequate water changes, builds up in the tank. Algae loves a high oxygen level and it produces more and more oxygen - far too much for the fish to consume.

Algae quickly succeeds in raising the oxygen level to 20 to 30 milligrams per litre. Contrary to popular belief, high levels are unnatural for fish. For most aquarium fish, the oxygen level of their natural habitat is between 2 and 3 milligrams per litre. Not only does the oxygen oxidises out the nutrients and vitamins that the fish and plants require, but the algae thrives in these conditions, to the detriment of the plants, which eventually perish due to the unfavourable conditions.

There are other factors that cause algae which include : excessive light, excessive phosphates, over feeding and over stocking.

So, how can you maintain an algae free tank.

1. The first and most important factor is the water quality. You must regularly change the water and keep the nitrate level low. I would suggest you change a minimum of 20% per month. If you can do this more regularly - even better. It really is no trouble of siphon 20% of your tank. Not only will your plants benefit but your fish will sparkle !

I use clear tube into a white bucket - old 2 gallon food containers are ideal. This enables you to check that no fish are sucked out through the tubing and you can easily observe it in a white bucket. Remember when replacing the water, do this gently with water of a similar temperature and with a tap water conditioner added to removed the chlorine.

2. You also need to keep the nitrate level under control. It always amazes me how many aquarists do not check their water for nitrates and nitrites. The dip-sticks make it simple and quick and if you are worried about the cost, cut the strips into two or three. Regular monitoring is vital. The way to deal with a high nitrate level is as follows : Partial water changes will dilute the nitrate levels. However, this will only take it down to the levels in your tap water. The most effective way is to run a nitrate removal resin in a Fluval 2 overnight, recharged in a bucket of salt water (for details see my article on maintenance) and repeat the process. I also run the nitrate resin in the water I use for water changes and try to bring it down to 20 parts per million. Anything lower and you will find your floating plants begin to suffer.

Other factors cause excessive nitrate. As previously mentioned, the other factors are : (a) over feeding, (b)over stocking, (c) over filtration.

(a) Over feeding is easy to control. The food manufacturers have a lot to answer for. Three times a day is ridiculous. Novice aquarists are very rarely shown how much to feed. Feed sparingly, once a day is sufficient. If you miss a day or two, fish in a planted tank will not starve.

(b) Over stocking is also easy to control. I recommend half the normal levels. A low stocking level reduces the burden of the biological filter and keeps the nitrate level down.

(c) Over filtration is the third main cause of excessive nitrates. A turnover of half to one times per hour is perfectly adequate. I particularly like the Juwel internal filter. Not only does it have a large filter area but a slow but efficient turnover. A heater incorporated into the filter gives good transference of heat throughout the tank. Remember when cleaning the sponges, always use tank water or you will kill the nitrifying bacteria. The planted tanks do not have air stones or spray bars. The extra oxygen is simply not needed and oxidises out the nutrients and causes the conditions that algae love.

Another method of controlling algae is to use plants that will rapidly leech out nitrates. This is where floating plants come into their own, especially important in a newly set up tank. Plants suitable to use are riccia, hornwort and Amazon frogbit. I would refer you to my article on Floating Plants for more detail. Not only do they leech out nitrates naturally, but they act as a physical barrier against the harshness of the new tubes and reflectors and give the other plants time to establish themselves. Also, fast growing plants, such as vallis, will help to keep the nitrates under control. Algae shrimps, flying foxes and ancistrius catfish are fun but only attack the surface of the problem. Water quality is all.

So, what about light. Excessive light, whatever spectrum, will cause algae. However, good light of the right spectrum for plants, of which there are many commercial products available, used sensibly, will be fine for your plants. The plants such as the ferns, anubias and mosses can thrive in natural daylight.

So to control algae, remember the golden rules :

1. Good quality water, low in nitrates.
2. Regular water changes
3. Don't over-stock
4. Don't over-feed
5. Don't over-filter
6. Always have a good covering of floating plants.

If you follow these rules, algae should be a thing of the past. Believe me, it works.

PETER BRADLEY

6.3.00