Lowers pH and makes aquariums more acidic. Fast-acting, colorless and easy-to-use.
Purpose and Benefits:
Directions for Use:
- pH Down is a liquid pH lowering product for freshwater aquariums. pH Down lowers pH by neutralizing carbonate hardness in the water.
- Adjusting the pH to the proper level will improve fish health, disease resistance, coloration and breeding. While many common aquarium fish will live in water with a pH range of 6.8 to 7.5, a pH of 7.0 is ideal for a community aquarium containing a variety of freshwater fish. Live bearers like mollies and swordtails prefer a higher pH of 7.2-7.6. Acid-loving fish such as angelfish and neon tetras prefer a lower pH of 6.5-6.8.
- Each dose of pH Down neutralizes some of the carbonate hardness and lowers the pH. The pH may rebound up to the original pH if the carbonate hardness is high. Several consecutive treatments with pH Down may be necessary to lower pH, but if there are fish present in the aquarium, the pH should not be changed more than .2 in a 24 hour period. The number of doses required to lower the pH will depend on the carbonate hardness level and the desired pH level. An aquarium with low carbonate hardness may require one treatment with pH Down while an aquarium with a high carbonate level will require several.
Compatibility: pH Down contains no phosphates and may be used with live plants.
- Use Aquarium Pharmaceuticals Freshwater pH test Kit to determine the pH of the aquarium.
- To lower pH, add two drops of pH Down for every U.S. gallon (3.78 L) of aquarium water.
- Take another pH reading before making the next addition of pH Down.
- If fish are present in the aquarium, do not change the pH more than 0.2 in a 24 hour period (for example, from 7.2 to 7.0).
How much pH Down will it take to lower my pH?
The amount of pH Down required to lower the pH of aquarium water depends on several factors. The primary cause of high pH is an elevated carbonate hardness (KH) level. Carbonate hardness, also known as alkalinity, is found in tap water and may also leach from aquarium gravel, ornamental shells, and coral. Each dose of pH Down neutralizes some of the carbonate hardness. It may take several doses of pH Down to neutralize enough carbonate hardness to lower the pH.
Why does my pH level drop after adding pH Down then bounce back up the next day?
pH rebound occurs when the carbonate hardness is high. Aquarium water with high carbonate hardness resists pH change.
Does pH Down contain phosphates?
No. pH Down contains no phosphoric acid or phosphates.
Can I add more than the recommended dose of pH Down?
Always follow the directions when using pH Down in the aquarium. Many aquarists treat a separate bucket of water with pH Down to adjust the pH before adding the water to the aquarium. Add as much pH Down to the bucket as necessary to lower the pH to the desired level. Once the pH has stabilized (12-24 hours), add the water to the aquarium.
Can I use pH Down in a saltwater aquarium?
Marine salts are formulated with a large amount of carbonate buffer to stabilize the pH. Each brand has its own unique formula and pH range. While adding pH Down to a saltwater aquarium is not harmful, it should not be used to adjust pH. Use Proper pH 8.2 to adjust and stabilize pH in saltwater aquariums.
Aquarium Pharmaceuticals Aquarium Supplies
Aquarium Pharmaceuticals (API) has been helping people take good care of ornamental fish for over 40 years. Their research and development scientists have advanced the care of fish with all-natural medications, stable bacteria for biological filtration, one-bottle test kits, consumer-friendly dosing caps and much more. They’ve received over 25 global patents for their breakthrough innovations in the aquatics industry. And they continue to look for ways to improve the fishkeeping experience for hobbyists. Research. Experience. Dedication to scientific, quality treatment for healthy fish. It’s what makes API the first choice of aquarium owners. API manufactures and sells hundreds of products across many different product categories, including aquarium and pond treatments, aquarium equipment, aquariums and fish nutrition.
We ship 99% of the products we carry for free within the contiguous United States using a mix of economy methods including USPS First Class Mail, SurePost and UPS Ground. Your order will arrive in 5-7 business days.
Over 90% of our members receive their orders within 2 business using UPS Ground. Upgrade from free economy shipping to UPS Ground for only $4.99—or spend $199 and we’ll upgrade you automatically!
Expediated shipping services are available for most products if you are in a hurry. Get guaranteed delivery in 2 business days, 1 business day, or next day by 10:30 am. Costs vary by location.
Same-day shipping is available Monday-Friday for most products—place your order by 10 am PST. Pre-ordered and back-ordered items do not qualify, nor do drop-shipped, live, or frozen shipments.
Learn More About Shipping
Return any new and unused item within 60 days for a full refund. Having difficulty with a product? Contact us to speak with an aquarium expert. If you need a replacement, fill out this form.
A small segment of the 180+ brands we carry require that customers contact them directly if/when problems arise. You can view the full list of those brands and get their contact info here.
Marine Depot is an authorized reseller for every product we carry. That means when you buy aquarium supplies from us, your products are not only backed by our own 60-day return policy, they also carry full factory warranties, where applicable. Some items have a 1-year warranty, others have limited lifetime warranties. Warranty coverage varies from manufacturer to manufacturer, so please read the product description of the item(s) you are considering thoroughly for details or contact us if you have warranty questions.
Learn More About Returns
Rack up reward points to earn discounts on future purchases! You can earn reward points by creating an account, writing reviews, referring friends, subscribing to our newsletter, buying products, and more!
- Most Products
Earn 5 reward points for every $1 you spend to get 5% cash back
- Marine Depot, AquaMaxx, Accel Aquatics, and Korallin
Earn 6 reward points for every $1 you spend to get 6% cash back
- Aqua Illumination, EcoTech Marine, Nano Box, Neptune Systems, NYOS, Oceanbox Designs, Pax Bellum, and Reef Glass
Earn 1 reward point for every $1 you spend to get 1% cash back
You can also get bonus reward points by purchasing select items during special sales and promotions.
Learn More About Rewards