The placement of Mercury in the 8th House for Aquarius lagna is considered to be an auspicious position. In this placement, Mercury is in its exalted state, which means it performs well and brings good results to the native. As a planet of intelligence and communication, Mercury here can bring transformative changes and significant gains to one's life.
Mercury rules the 5th and 8th houses in this placement, making them prominent areas of influence for the planet. The 5th house represents education, creativity, children, and speculative gains; while the 8th house symbolizes transformation, sudden gains and losses, hidden knowledge and mysteries.
With Mercury being the ruler of these two houses, it signifies that individuals with this placement are likely to excel in fields related to education such as academia or research work. They are creative thinkers who possess an analytical mind with an ability for sharp reasoning. Individuals may develop an interest in subjects like astrology or spirituality due to their natural inclination towards deeper understanding.
Moreover, this placement holds benefits for those looking for speculative investments as well. It can bring sudden gains through stock markets or other trades related activities.
Being a natural karaka of the fourth house representing home-life, comforts, vehicles; and tenth house representing vocations/ career path & professional life - individuals will experience positive results with regards to family life and at their workplace too. This translates into a harmonious co-existence between work-life balance with enough time dedicated for familial duties without disturbing professional success.
In addition to its own house's significance being taken care of by mercury itself; Its aspect on second house also greatly helps individuals with capabilities like rational decision making grounded upon pragmatism & great monetary profits from self endeavours indicating good financial stability throughout life.
However there could be some negatives too - such as over analysis may get magnified if individual already has tendencies towards negative thoughts or overthinking patterns resulting in mental stress. Health may also face issues related to the reproductive system, stomach or lungs- hence medical attention needs to be taken promptly.
On a concluding note, while it's important to take birth charts as a whole rather than one specific placement. The mercury-mahadasha can bring positive results for those with this placement during their life span of 17 years. It is advised to consult an Astrologer for more personalized analysis and guidance based on other planetary positions and inter-play in natal chart for further accuracy.