I have had a 5 gallon aquarium I set up to learn the hobby. Its RO water with quartz gravel and no CO2 injection (Low tech). it has always had algae. Only for a short has it worked well with minimal algae but it didnít last and I have tied every suggestion people have given to others and nothing has worked. Even EI dosing has not worked. The aquarium collapsed early this year When the algae rapidly took over the tank in three weeks.
I started to think about my tank one day and successful tanks using the EI method (which I have tried unsuccessfully) it occurred to me that maybe algae had specific nutrients plants don't need. So I started searching the web and quickly found that it was true.
The commonly accepted elements plant need are:
N, P, K, Ca, Mg, S (Macros)
Fe, Cl, B, Mn, Mo, Zn, Cu, Ni (Micros)
Note all Abbreviations for the elements correspond to the periodic table of elements
What I found is that in addition to the plant elements Algae needs Co (cobalt, Se(selenium), I (iodine) and V (vanadium), and Br (Bromine). i call these Algae Specific nutrients (ASN)
Plants no longer need ASN elements to grow due to evolutionary changes they needed to move out of the ocean and onto dry land. However plants haven't forgotten about ASN. Some plants still use iodine and selenium and cobalt but in different ways and they can continue to grow even when ASN elements are not available.
So based on this information algae should not grow in DI water with all the plant nutrients. I did multiple test in a small container and indeed found that algae would not grow. I also did another test and did find that with the fertilized DI water and ASN added algae Algae did grow. Also my research online indicates Cobalt and selenium at high levels are toxic to pants and animals.
Based on this I stopped using Flourish ,which has Cobalt, and used CSM+B plus my own macro mix that contains N, P, K, Ca, Mg, S, and CL. I also use a DI filter to lower the TDS of my RO water to about 1ppm TDS. Algae is no longer growing in my tank. It can now take weeks for any new algae growth to become visible. In the past I was removing a fist full of algae almost daily.
Unfortunately I ran into the toxic properties of CSM. Duckweed is growing but my plants are not. I will try making my own micro mix in january based on the information in the custom micro mix thread on this site.
However based on what I have found it is now obvious why Estimative index tanks generally have minimal to no algae growth. With no Algae Specific nutrients added in the fertilizer algae will quickly run out of the ASN nutrients while the plants will continue to grow. Shrimp and snails will then consume much of the algae or it will simply die off. However if your fertilizer is deficient in one plant nutrient plant growth will slow or stop and Algae Specific nutrients (ASN) will start to build up and algae will then start to grow.
Also note that when you have a lot of algae in the tank you are likely to have nutrient deficiencies. My experience and water test have confirmed that algae can consume plant nutrients extremely rapidly and can create multiple nutrient deficiencies that will slow or stop plant growth.
Based on my experience I would not recommend using fertilizers with Algae Specific Nutrients: Some Examples of fertilizers with cobalt or vanadium:
Bright well Aquatic fluorinmulti plant care
Prior to learning about ASN I was using the Flourish Comprehensive (Cobalt only) and when I was doing EI dosing I was using Flourish Trace (which has Cobalt and Vanadium). While some people do use these successfully it is always possible to get a tank crash like I had. Also note it is not possible to prevent any ASN from getting in the tank. Tap water will have at least some of these nutrients or all of them. Animals also need ASN nutrients. Any any balanced fish food will have ASN elements in it.
Note below are some links I found helpful in identifying ASN elements. Unfortunately I lost or didn't save all the links I found helpful in my research.