Hi,
As is constantly being argued, there are different paths to success and there are many factors and variables. This guide that you referenced suggests to add fauna on the third day, which for an experienced hobbyist, can work, but for a beginner is a terrible idea. The author also makes this statement which is patently misleading:
Put shrimps and snails into the aquarium to prevent algae problems. We recommend 1 Amano shrimp per 5 litres of water in the start-up period. You might also add e.g. posthorn snails and other shrimps that also eat algae (see list of algae eaters
here). Be aware that the legislation in your country perhaps prescribes that you cannot put animals in the aquarium until later after the start-up.
So you question why we challenge this aspect of Tropica's 90 day plan.
I will challenge you with this:
Do you believe that shrimp and snails can actually prevent algae from forming?
If you search this or any forum will find any solid evidence of fauna preventing algae?
My belief is that algal blooms occur as a direct result of poor plant health due to mismanagement of plant husbandry. I believe you will find that in a vast majority of cases, your forum search will reveal that no amount of fauna has ever prevented algal blooms, and that at best, fauna in the tank can mitigate the volume of algae in the tank.
I believe that algal blooms cannot appear simply as a result of a shortage of fauna in the tank. Further, there are algal types that fauna will even not touch.
I believe therefore that it is folly to depend on fauna to prevent algae and that you are actually endangering the health of the fauna by placing them in the tank under such unstable chemical conditions. What's more, fauna in the tank handcuffs the hobbyist by disallowing certain measure to be taken to reduce or eliminate problems in the tank. There are chemical reactions that occur in the tank that you cannot see, but which damage the fauna. It may not kill them outright, but it can do permanent damage to their ability to resist pathogens or to deal with chemical attack in the future. Subsequently, the fauna often perish under "unknown" circumstances and blame is then placed on unrelated factors, such as "high TDS" or "high Nitrate".
If they had moved this step of placing shrimp in the tank to day 90 it would be less objectionable.
Of course, no one wants to wait 90 days to put fauna in the tank, so I believe this instruction panders to the impatient hobbyist.
Has it worked for some? Yes, absolutely.
Is it based on a sound principle? I say No.
Cheers,