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Note by Editor: these articles are received in German. I translate them and post them and then go over the text again and add what I may have left out the first time around to get the article on the web site faster. This is an update and now includes all of Martina's German text including some additional material sent to me by email on 6/25/97.
Somehow, even though we may not be aware of it, the phosphate levels dissolved in our aquarium water have a tendency to rise unless, of course, we do something about their presence. This is especially true when an aquarium has not yet aged for long enough. It also happens in aquariums that are not operated using the more recent reef aquarium principles.
By not using such principles I mean that the aquarium is either a fish-only tank with dead coral in it, or it is a reef tank that does not use the live sand and/or the liver rock method of filtration. As far as I was able to tell there are quite a few of these of http://www.athiel.com
Phosphates are present in the aquarium in many forms. The one form we are interested in most, is ortho-phosphate. That is, indeed, the chemical form that algae can very easily use as a nutrient for growth, and do. Even though there may be complex and complex ones of organic or non-organic nature, they eventually all break down to ortho-phosphate, given enough time.
When the levels of dissolved PO4 rise above 0.03/4 ppm, the likelihood is high that micro-algae will start to appear in your aquarium. High is probably not the correct word to use as at such levels micro-algae will appear for sure. That has been my experience and that of many others I know in the hobby here.
By micro-algae I mean any type of algae that we consider as undesirable in the aquarium, whether hairy, crusty, encrusting, filamentous, slimy and so on. Anything that we would consider a weed if we were talking about a lawn or garden.
You may very well still believe that nitrates are the main cause of this algal growth because older literature has so often intimated that nitrates are the culprit. Although nitrate does contribute to algal growth, phosphates are a far greater reason for their appearance and proliferation throughout your aquarium. Nitrate levels that are high are certainly not desirable but they appear to affect other matters in the tank more than actual algae growth (color and appetite seem to be affected in fish, and in corals not opening as wide appears to be a consequence of high nitrate levels).
You can test this is you wish by loading your tank, and overfeeding, so phosphate rises quickly, or you can take my word for it. Make the levels rise to 0.05 ppm and you will see that micro-algae of all kinds appear. I am not suggesting you should but if you are into "seeing is believing" then that would be the way to go about it.
As far as I was able to determine, Thiel was the first one to point out that phosphate was the problem and I believe his company was the first one to come out with a product. compound I should say, to absorb phosphates. Who was first is not that crucial though, the key is that phosphates give rise to micro-algal growth. By now, I think, just about everyone is aware of that. I have found my personal email with him very informative and a good learning experinence but draw on knowledge from others as well and add to that what I discover myself. I certainly do not rely on just one source of information as that would lock me in to one person's theory and that would be sort of like creating tunnelvision after a while.
To keep our aquariums free of algae we can use several methods (I described them in another article I wrote). All those methods dealt with the outcome though (the algae) and notwith the cause (the phosphate).
The article refered to, explained how to rid the aquarium of algae and how to lower phosphates and suggested a combination of methods to arrive at that result. Still the key is to understand that to really solve the problem one needs to eliminate the cause of the algae growth and not just the outcome of too high levels of PO4 (the algae).
The real problem we need to overcome however is the build up of phosphates in the aquarium water and we need tofind the reasons where they come from. That is the aim of this article: determining the causes of phosphate increaeses. I cannot offer solutions for each of the sources of phosphates as that would make this article much too long. If you look at all the causes though, you can start determining whether they apply to your aquarium and whether you should do something about them.
There are many reasons for phosphates to appear and then be present in the water, both external and internal ones.
It should be pretty obvious from the above that there are a multitude of reasons why phosphate appears and rises in concentration in the tank. I have listed some obvious ones but the list is by no means complete.
It would be too lengthy to give you a plan of action that you can take for each of these cases. Suffice it to say that all of these possible causes need to be carefully looked at in your situation. Testing may have to be done to determine whether, indeed, an additive is phosphate free for instance. You may need to test your raw water and the salt you are using, and so on. Test your tap water, test the water coming out of RO or DI units and make sure that the PO4 levels are near zero (you will need a test that measures in the 0.0x range to determine that).
Being aware of the possible causes is half the battle won! Taking action and eliminating the phosphate producing ones will allow you to get a handle on the problem. Doing so regularly will eliminate unwanted algae from your aquarium. Keeping some hermit crabs in the tank will help even more, but in my experience you do not want to have so many that they are starved for food and may become more aggressive, as explained in my other article.
Awareness of the fact that very low levels of phosphate lead to micro-algal growth is a definite step in the right direction. Many of used to think that several parts per million was a low concentration. It turns out that Thiel, and others after him, have proven that wrong. Levels lower than 0.1 ppm are already too high. Ideally you wish to maintain your phosphate concentration at 0.03 to 0.04 ppm.
As a last note: test your phosphate levels on a regular basis as it does not take much for their levels to suddenly rise about the safe zone. One small animal dying in the tank, or overfeeding a few times can easily lead to levels that are higher than the suggested levels. Also, in reef tanks, additional die off on some of the rock can increase PO4 in the tank's water. The more often you check, the better of you will be as you will have the chance to intervene and lower the levels before algae start to appear all over the tank.
The algae dealt with in this article are for the majority green in color. If you run into red slime algae, you have a different problem. Cyanobacteria are the cause. I noticed that the Thiel web site has various articles already on how to deal with thatsituation. The same applies to silicates which lead to the appearance of brown diatoms. You may wish to read those articles to get a more complete picture of the algae situation in aquariums.
Whereas macro-algae may be considered desirable by some, this is a totally different topic. Of course macro-algae will feed on phosphates too. The low levels recommended and a small iron supplementation will make them grow and spread if that is what you wish to achieve. Remember though that many corals react negatively to the close presence of some types of macro-algae (Caulerpa types in particular).
From what I know, Thiel has done a lot of research on macro-algae so if you have any questions regarding them you may wish to join his mailing lists on his web site http://www.athiel.com and ask him questions. When I last visited him in Connecticut and that is a few years ago he already had close to 100 books on algae and phycology alone, not to speak of the hundreds of others on any sugject you can think of that is closely or remotely related to the hobby.
Chuus as we say in Germany
Martina Rodacks