I think I will start EI, is that generally better to reduce algae along with the right co2 level ?
Hard to say.... To be honest, I will make quite impopular myself here by telling this by the look of it, but I call EI system the "shotgun approach": We do not have a real idea about the plants in our tank will need, so we just overdose the tank following an overall NPK index and trace elements enough to ensure unlimited growth, cross our fingers, and make regular and frequent significant water changes to ensure our excess does not cause algae. The system works, no doubt, but a single misstep and you get wonderful algae problem and/or melting plants. There is no guarantee EI system will solve your algae problem. However, it is true that it is the better system for those who are not trying to get equilibrium in the tank, and just get the plants right. These concept are separated ideas, in my point of view.
Algae are common during the first days of your tank, and any established system tends to have this problem. This is normal if you think about: Plants are not in optimal conditions to use nutrients in water, and in general any excess of N in the tank in the earlier stages of your tank will lead to diatomea or cyanobacteria. However, the problem solves itself once the plants take control of the chemistry of the water. If you have other types of algae, then the problem can be more difficult to eradicate and might be due to a combination of factors, that could be many: light, deficiencies in some nutrients (usually K, traces, or CO2), lack of cleaning in the tank, or just that the sort of plants you use are not requiring what you expect. In this forum about algae you will find many ideas respect to how to fight algae, which depends on your setup as well as in the type of algae you have. It is a good reading to learn about it.
In general:
-Reducing light helps to reduce the amount of algae but does not solve the problem itself. Unless you correct the subjacent problem, the algae will be back as soon as you reestablish your normal cycle of light.
-Water changes are intended to "reset" your system. You can potentially have an excess of nutrients so you need to ensure that you correct this problem. Water changes are the answer in this case and help to get control about what happens in your tank.
-An excess of nutrients what really means is that you have too many nutrients for the levels of light and/or CO2 in the tank, and/or density and types of plants. Light can be a limiting factor of growth, and at the end, what is really counting is the combination of light, CO2, and nutrients balance fitting the needs of the plants you have in your tank.
-From the above, it is deducted that regarding nutrients the problem is not the excess but the "balance". Answer to algae is to get that balance, and there is no master answer for that, because that depends on many factors, not always under our knowledge. To fight algae you have to try different things until getting this balance, which will be different depending on the tank, soil, rocks, plant composition, etc. One of the reasons why EI works for many people is because the constant reset of the system through water changes, so good luck when you go on holidays for two weeks!
-Introducing some livestock fancying algae helps to keep them in bay (e.g.
Caridina Multidentata and
Otocynclus sp.)
-Cleaning the tank and filter, to avoid organic wastes transforming in nutrients and unbalancing your tank, it is a good preventing practise.
-Aireation helps, especially if done during the nights.
-Introduce fast growing plants, which is more or less the same than reducing the time your nutrients stay in the water column, i.e. reducing your nutrients level, anyway.
Despite of this, which are general rules, the only way to solve it is through experience and essay/error. Do not give up, adjust the most likely elements causing the problem, and within the time you will hunt down the problem, but be persistent, because algae are. You can see many successful people here, so be ready for the fight!
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