Mermaid oil comes directly under the Red's domain so it is imbued with with her particularly sharp and aggressive energy that's prominent in the other oils that she claims as well.
Mermaid oil can be used for drawing clarity and insight on situations by cleansing away confusion and mental fogginess. You may develop sudden "aha!" moments where answers appear to questions you had or didn't realize you actually needed answered first. This is an oil of psychic defense.
Mermaid oil can be used to displace evil influences and draw in a vigorous, uplifting vibration to you or the space you're using it in. It will alleviate dark moods and help you surpass feelings of guilt and shame. Additionally, it helps wards off illness. You may find it helpful to burn this oil on candles in your bedroom to keep sickness at bay.
Mermaid oil can be used to bring balance and harmony to your throat and heart chakras. You gain the ability to speak your truth and with compassion. If you need to speak up for yourself or have difficult conversations, apply daily for 7 days.
It adds a touch of sweetness to every ritual you do. 
And, of course, Mermaids love to bring you money (and love, too, but the Red cares less for love and more for money so same, sis🤷🏾‍♂️), so use this oil for asking money and luck to flow swiftly into your home, life, and purse. Use as you would any other money-related oil, but note that any financial blessing from this oil is expected to be used wisely rather than frivolously. 
Wear Mermaid oil during prayer/meditation to connect deeper with your mermaid guides and their magical teachings for you. They may even come to you in dreams and teach occult secrets. 
Use Mermaid oil to soothe emotional turmoil and aid in spiritual growth. 🧜🏿‍♀️
MONEY: You can use it like any other money oil and rub it on wallets, desks, computers, mojos, cash, checks, letterheads, bills, and so forth as well as candle work and oil lamps. 
CANDLE WORK: Blue candles for spells of truth, devotion, creating a river of opportunities. Green candles for financial luck and growing water-based plants. Pink candles for personal attraction and purple for increasing personal power and psychic energy.
SPIRITUAL BATH: Add a drop of Mermaid oil to Moon water that's been charged under the Full Moon. Add this mixture to your bath to purify your spirit and compel the truth from others. Remember to air dry.
If you need clarity or insight on a situation, Mermaid oil is especially suited for helping clear your mind of disruptive thoughts and feelings. It keeps the blues at bay if you use it when feeling down or stressed. Anoint your temples and go to a body of water such as a lake or river and pray for clarity, answers, or resolutions to your concerns and questions.