Choosing a Date to Open a Shop and Keep Fish: BaZi or Wealth Position?

Friends opening aquarium shops, teahouses, or convenience stores often ask the same question before opening day: there are fish to keep in the tank and a date to pick for the door opening—should this be based on the shop's Wealth Position, or on the owner's own BaZi (Four Pillars of Destiny)? Some people try to cover both bases, having someone work out the BaZi and someone else check the Wealth Position, only to end up with two conflicting opinions and no date settled for ages.

This question actually conflates two separate matters. Date selection and Wealth Position are not governed by the same thing.

Date Selection Governs Time, Wealth Position Governs Space

Let's separate the two matters first.

Selecting an auspicious date for a shop opening is about choosing a point in time—which day to open, which hour to cut the ribbon. The core of traditional date selection is making sure this point in time is compatible with the person opening the shop. So when an old-school master calculates an auspicious opening date, the first step is always to look at the shop owner's BaZi, especially the Day Pillar. The Heavenly Stems and Earthly Branches of the chosen day must not clash with the owner's Day Pillar or Chinese Zodiac sign. Someone born in the Year of the Rat should avoid a Horse day for opening; if the Day Master is inherently weak, pick a day whose Five Elements (Wu Xing) support and strengthen the Day Master. This is the root of date selection—discussing which day is good without reference to the person is just empty talk.

Wealth Position is a different matter entirely. It is a spatial concept, referring to which corner of the shop gathers energy and favors stillness and stability. The most commonly used is the Ming Cai Wei (Visible Wealth Position), the corner diagonally opposite the entrance—this applies regardless of whose shop it is or what the floor plan looks like, and it's simple to locate. For something more refined, the hidden Wealth Position can be derived from the building's orientation, but that requires Flying Star calculations, which ordinary people are prone to getting wrong on their own.

Where to place the fish tank falls under the category of Wealth Position, and has nothing to do with which day the shop opens. Water has long been regarded in folk belief as something that can bring wealth and stir energy. A fish tank belongs to the water element, and placing it correctly helps activate the Wealth Position. But what it activates is that space, not that date.

So these two matters run on different tracks—one along the timeline, one within the space. How to set the opening day depends on BaZi; where to place the fish tank depends on Wealth Position. Neither can substitute for the other.

For the Opening Date, the Shop Owner's BaZi Takes Priority

When it comes to actually picking the date, here's the order of operations.

First, determine the person. Generally, whoever is funding the shop, running it day to day, and managing the books is the one whose BaZi should be used. For shops opened in partnership, tradition holds that the BaZi of whoever holds the largest stake or actually manages the business should be used—it's impossible to accommodate the BaZi of five or six people at once, since no date would ever satisfy everyone.

Next, chart it out. Take the shop owner's BaZi and compare it against each candidate date one by one, first eliminating any days that clash or conflict. Then look at the Twelve Officers of Jianchu—days like Open Day and Completion Day literally carry meanings of opening and accomplishing things, and are commonly used for shop openings in folk practice; days like Broken Day, Closed Day, and Danger Day clearly don't suit the tone of an opening and should be avoided outright.

There are also several hard taboo days to steer clear of regardless of how well they match the BaZi. Yang Gong Ji (Yang Gong's Taboo Days), Yue Po (Monthly Breaking Day), and Shou Si Ri (Day of Received Death) are all clearly marked on the traditional almanac and are universally recognized as inauspicious for shop openings. Even if your BaZi matches well, these days are not recommended.

The hour is settled along with the date. Once the day is chosen, pick an auspicious hour within that day, avoiding the hour that clashes with the owner's Hour Pillar. Opening the doors to greet customers, setting off firecrackers, and the first transaction of the day should all fall, as much as possible, within this auspicious hour.

I've seen quite a few people fix a date just by spotting the line "suitable for opening a business" on the almanac, without considering their own BaZi at all. The suitability notes on an almanac are general guidance meant for everyone, and don't factor in you as an individual. If you really want to do this properly, the BaZi layer needs to be added in—otherwise you might end up picking an "auspicious opening date" that actually clashes with your own Day Pillar, which rather defeats the purpose.

Keeping Fish Falls Under Wealth Position and Feng Shui

As for the fish tank, from start to finish it's a matter of space.

Location first. The diagonal corner that is the Ming Cai Wei is the common spot for a fish tank. If the shop's orientation is clear and someone is willing to calculate it in detail, the hidden Wealth Position can also be found, letting the tank activate that position. The tank should not face the main door directly, since the energy of the water gets scattered by the airflow right at the entrance and cannot gather; it also shouldn't be placed too high, above head level—in folk terms this is called "water pouring over the head," and is considered inauspicious. There's also a point many people don't know: the fish tank should not be placed directly beneath a Cai Shen (God of Wealth) statue, since Cai Shen favors purity and stability, and a sloshing tank of water underneath creates a clash.

As for how many fish to keep and what colors, folk traditions vary. Commonly heard advice favors numbers like one or six that correspond to the water element, and colors like black, white, and gold. These sayings come from various sources and aren't fixed in any authoritative classical text—treat them as a way to invite good fortune and please the heart, not as hard rules to be scrutinized. Replacing a dead fish promptly, and not letting the tank water turn murky or foul, matters far more than numbers or colors—a tank of stagnant, dirty water sitting in the Wealth Position carries no good omen at all, whatever the numbers say.

So should the fish tank setup also follow a selected date? If you want to be thorough, some people do pick a water day or the shop owner's auspicious day for the first filling of water and introduction of fish, known as "starting the tank." But this is an added touch, far less weighty than the opening date. If priorities must be set, settle the opening date first according to BaZi, then schedule the tank-starting time afterward—simply pick a convenient moment a day or two before the opening. Don't let the lesser matter override the greater one; it's not worth throwing the opening date into disarray just to accommodate the timing of adding fish.

Back to the original question: date selection is tied to the shop owner's BaZi, while fish-keeping and tank placement are tied to the shop's Wealth Position. Handle the two separately, each governing its own domain, and they won't conflict. What really causes trouble is using the fish tank's position to decide the opening date, or using the opening almanac to decide where to place the fish tank—that's where things truly get tangled.