Ark said:
thanks james but dont adding ferts and increasing light time increase the risk of algae
Hi Ark,
Studies over the past decade have shown that there is no correlation between nutrient levels and the inducement of algae. In fact the data indicates just the opposite; Failure to feed the plants properly always results in algae. You need merely look at your present situation to see that algae is a symptom of poor plant health. If you focus on feeding your plants and getting them healthy you will discover that you will be able to keep algae at bay.
Because your tank size is at the smaller end of the scale it's difficult to judge an accurate wpg and so on but it is very easy to develop a dosing scheme that will guarantee the health and development of your plants.
I and others typically use the dry salts sold at AquaEssentials but commercial aquatic fertilizers work just as well if a bit more expensive. I would suggest the following dosing scheme to begin with:
3X per week
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1/16th teaspoon (0.4 grams) KNO3
1/64th teaspoon (0.1 grams) KH2PO4
2X per week
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1/32 teaspoon (0.1 gram) CSM+B or alternatively use any trace element mix dosed per instructions on the bottle.
50% water change should be done at least weekly and you should clean out any detritus.
James also suggested the use of Excel which is very helpful in providing a carbon source and does have some algaecide properties. Depending on which plants you have (some plants such as Riccia respond poorly to it's use) this is an excellent source of carbon and a brilliant alternative to yeast based CO2 injection. It is an expensive option however.
Now, having said all that it's important to note that it will take about 2-3 weeks for the plants to regain their health and dosing now will not now make the algae disappear. Once algae is induced it then feeds on any nutrients that are present in the water. Once you start dosing therefore you may actually see more algae. This is the Catch-22 which led many people to the conclusion that nutrients cause algae. In fact it takes time for the plants to recover but there is only one way to accomplish this and that is to feed them. Algae that does appear has to be manually removed. Individual leaves that are coated with algae indicates that particular leave has succumbed and must be removed immediately. It is labor intensive but after a few weeks you'll see new shoots sprouting indicating that the plant is responding. As you continue to feed you'll find that less and less algae returns.
Cheers,