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re: phosphate and algae growth

     Luvskribs at aol_com writes:
     
     >> it was suggested to use Osmocote as a fertilizer for aquarium 
     plants. Wouldn't the phosphorus in it contribute to unwanted algae 
     growth? <<
     
     Conditions favorable to plant growth also are good for algae. An 
     excessive of any nutrient especially phosphates or nitrates can lead 
     to conditions where the most rapid growth plant/algae will flourish. 
     Guess what that is? Yes, algae!. When there is a balance of all 
     nutrients, CO2 and light, then the large plants will be able to 
     outgrow the algae. You can avoid some types of algae by not 
     introducing it (e.g. sterilizing new plants using a mild bleach dip) 
     but other types like green water and cyanobacteria can spread by 
     spores in air or exist in natural soils.
     
     Osmocote is a slow release fertilizer and IF used, I recommend putting 
     it inside clay balls to further slow its release so that the plants 
     will have the greatest opportunity to get it using their roots. It is 
     entirely possible that if you are adding other nutrients, the one 
     which is limiting the growth of your plants is phosphorus. That's not 
     necessarily bad because you may not want your stem plants to grow too 
     rapidly. On the other hand, richer substrates (richer than plain 
     gravel) do wonders for Crypts, Echinodorus (sword plants) and other 
     crown plants.
     
     Another strategy for algae control is to try to reduce the amount of 
     iron (Fe) available in the water and maximize Fe availability in the 
     substrate. This is the advantage of laterite and other soils! If you 
     have filamentous algaes present in your tank and you overdose on 
     chelated Fe, no matter how religiously you have reduced the 
     phosphates, you will almost certainly get a nasty algae problem. An Fe 
     concentration of 0.1 ppm chelated Fe is considered sufficient for 
     plants and won't encourage algae growth. It probably won't make 
     existing algae go away however. You do that with your scissors and 
     scraper and filter (to get the loose pieces you dislodge). I'm not 
     recommending you to add fertilizers unconditionally; YOU must make 
     that decision based on informed observations. First you should master 
     growing plants without algae and then you can experiment with 
     optimizing the conditions for your favourate plants. Sometimes beating 
     algae means you must provide a good balance of nutrients for your fast 
     growing plants so that they grow rapidly and fill the tank.
     
     By the way luvskribs is not your real name is it? Most folks here go 
     by their first names! I don't care if the email address works; you 
     must just fool the junk mail robots. Ditto George's comment "get a 
     name!" ;-)
     
     Steve P in Vancouver