Every tank is different and will react differently to the zeo method. The heart of the ZEO method is the ZEO filtration media. The media is placed in a special reactor which allows you to raise and lower the media in a fluidized chamber. The chamber allows bacteria to colonize the media. The media itself absorbs ammonium which prevents the nitrate cycle from beginning (Ammonium --> Nitrite --> Nitrate). The zeobac is the bacterial additive. Zeostart 3 is the carbon source. I no longer use the zeofood since it causes issues with algae when combined with AAHC. I use Extra, Zeozyme, Biomate, Coral Vitalizer, ZeoSpur, AAHC, and Coral Snow. Each product has a different purpose and can be explained further in the zeo guide.
So how can ZEO wipe out your tank? First let me explain in general terms what ZEO does. The FULL ZEOVit system brings your tank to an ULNS state and will keep it there. You can wipe out your tank by stripping the tank of nutrients too quickly. You will see rtn beginning at the base. This is easily achieved when too much media is used or the flow through your reactor is too fast. You can also cause your corals to become unhealthy. This causes them to become susceptable to issues that a healthy coral could withstand. A great example of this is when my corals began to shed flesh after being removed from the tank for maintenance. After I placed them back in the tank the flesh just floated away. Certain products like ZEOSpur can cause the flesh to become thinner and thinner over time. Eventually the coral will starve/bleach due to the lack of zooxanthallae or coral tissue.
Please know that you can use some of the zeo products without using the full zeo system. See Connie's post above.
Warmest Regards,
James