Can You Use Aquarium pH Down Or pH Up For Hydroponics?

There are a lot of hydroponic growers out there wondering whether to use aquarium pH down or up for their hydroponic systems. It’s pretty confusing to be honest, especially when both solutions tend to work the same either in an aquarium or a hydroponics nutrient solution.

So, can you use aquarium pH down or up for hydroponics? Aquarium pH buffers have the same chemical formula as hydroponic buffers, and hence, can be used to buffer nutrient solutions easily. However, there are pH buffers with some chemical formulas that result in negative side effects for any hydroponic system.

I have seen a dozen of people wanting to use aquarium pH buffers for their hydroponic systems. whether they are trying to buffer the pH using the same bottle, or they can only find an aquarium pH buffer at their local store, they do have a point here.

There are several types of pH buffers available in the market, and each product can be made from an entirely different chemical formula than the other available ones. Some chemical formulas do have side effects when it comes to using them with hydroponic nutrient solutions.

Using Aquarium pH Down For Hydroponics

As I have mentioned before, aquarium pH down can be used with hydroponic pH buffers as long as they have the same chemical formula. pH down buffers can be based on different chemical formulas.

The most widely used chemical formulas are:

  • Phosphoric Acid
  • Nitric Acid
  • Citric Acid

The Suitable Aquarium pH Down For Hydroponics

Phosphoric And Nitric Acid

The majority of the pH down buffers for hydroponics are made of phosphoric or nitric acid. They tend to have no negative side effects and produce efficient results when it comes to lowering down the pH.

So, if your aquarium pH down solution is based on either phosphoric acid or nitric acid, you are good to go.

Unsuitable Aquarium pH Down For Hydroponics

On the other hand, some aquarium pH down buffers does have citric acid as their main active ingredient. Citric acid is safe to be used when it comes to aquariums, but if you want to use it for your hydroponic system, you will have to think twice.

Citric Acid

Citric acid tends to be weaker than the other main ingredients. You will need to use a higher dose to produce the same effect as that made by phosphoric acid. But unfortunately, this doesn’t stop here. Citric acid can produce major side effects when used for any hydroponic system.

High concentrations of citric acid tend to promote bacterial growth; citric acid can be a part of the bacterial cellular energy metabolism. As a result, the bacteria will use it as a food source to produce energy and further reproduce forming a huge bacterial colony in your nutrient solution.

Using Aquarium pH Up For Hydroponics

Just as pH down buffers, aquarium pH up products can be based on different chemical formulas. The most important thing is to make sure that the used chemical formula is compatible with hydroponics.

The most widely used chemical ingredients for pH up buffers are:

  • Sodium Bicarbonate
  • Potassium Hydroxide
  • Silica

Unlike the aquarium pH down, the main ingredients used in making pH up buffers don’t have huge side effects on the majority of the hydroponic systems. However, there are some chemical formulas that suit hydroponics better in terms of how long they last and their direct effect on the plants.

The Suitable Aquarium pH Up For Hydroponics

Potassium hydroxide and silica-based pH up products do represent a huge chunk of the hydroponic buffer market. That’s why I do recommend that you can use any aquarium pH buffer that is based on the previously mentioned chemical formulas.

Potassium Hydroxide

Potassium hydroxide has no side effects on hydroponics. However, they can be extremely irritant to the human lungs and can sometimes result in pulmonary edema, so, You have to careful when using potassium hydroxide based pH up products.


One of the best chemical ingredients to be used, especially for hydroponics, is the silica-based pH up products. Silica buffer products will last longer when it comes to regulating the pH of any nutrient solution. This will eliminate the pH fluctuations that usually happens two days after you have already set the pH of your hydroponic nutrient solution.

Another great advantage is that silica tends to provide more nitrogen for the plants. This will significantly improve your plant’s ability to manufacture chlorophyll molecules leading to better photosynthesis, and thus, better overall growth.

Unsuitable Aquarium pH Up For Hydroponics

Sodium Bicarbonate

Don’t get me wrong, I know that sodium bicarbonate has been frequently used before in regulating a lot of hydroponic nutrient solution whether in a pH up buffer product or just in the form of baking soda at home.

But what I really don’t like about sodium bicarbonate is that after several uses, it tends to produce a lot of salt build-ups that I have to regularly clean in order not to mess up my hydroponic system. So, why I would use sodium bicarbonate when there are great alternatives like silica and potassium hydroxide.

If you only have sodium bicarbonate based products at the moment, then it is fine to use it but you will need to flush your system more frequently in order to get rid of the excessive salt build-ups.

On the other hand, if you are looking to buy a pH up product to be used for both, your hydroponics and aquarium tank, then I advise you to use any silica or potassium hydroxide based pH up the product.


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  1. Pingback: Ph up and down for fish - Taunt On Water

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