Can I use ACID BIO in hydro if I don't have ACID PRO?

In a pinch, yes — but it is not ideal. Organic acids can feed biofilm in reservoirs and drip lines of closed recirculating systems. For hydro and coco, ACID PRO (mineral) gives a more precise and stable correction with no risk of adding carbon to the solution.

What exact pH should I target in coco?

5.8–6.2, with 6.0 as a solid starting point. Below 5.8 you start limiting calcium and magnesium uptake; above 6.2 iron and manganese availability begins to drop.

My solution pH is correct but I still see deficiency symptoms. Why?

Solution pH is not the same as root-zone pH. In soil, the pH right at the root can differ by several tenths. It is also possible your meter is out of calibration — the most common cause — or the deficiency is of a nutrient less dependent on pH, like calcium under high VPD.

How often should I adjust pH in soil?

Once a week is usually enough. The organic matter in the substrate acts as a buffer and dampens swings much faster than a hydro system. Monitor runoff pH, not just the pH of the solution going in.

Does the pH regulator add nutrients?

Not in any meaningful way. ACID PRO and ACID BIO are formulated to correct pH, not to feed the plant. They may contribute trace ions from the acid itself (phosphates if phosphoric acid is used, for example), but the dose you use to dial in pH does not replace any of the nutrients in your base feeding program.

pH Regulators: When to Use Mineral vs. Organic

Why does your feeding pH target change depending on substrate?

In true hydroponics there is no organic matter to buffer the solution — every change in the reservoir hits the root zone directly. That is why the target range is tighter and more acidic (5.6–5.8). Coco is also inert but has some cation exchange capacity, so it tolerates a slightly wider range (5.8–6.2). Soil with organic matter acts as a natural buffer around the root zone and works best between 6.0 and 6.5.

Hydro (NFT, DWC, aero): target pH 5.6–5.8. With no substrate buffer, a 0.5-unit swing can lock out a micronutrient within hours.
Coco: target pH 5.8–6.2. Coco fiber has no real buffering capacity, but its CEC holds some cations near the root zone.
Soil with organic matter: target pH 6.0–6.5. Organic matter and soil microbes stabilize pH around the root; dropping below 6.0 starts to inhibit that biology.

What happens when pH drifts out of range?

pH is not a cosmetic number — it determines the chemical form of every nutrient in solution and whether the root can actually absorb it. Above pH 6.5 in hydro/coco, phosphates begin precipitating with calcium and magnesium, and iron and manganese lock out even when they are present in the reservoir. Below pH 5.5, iron and manganese become excessively available and can accumulate to toxic levels (Velechovský et al. 2024, Front. Plant Sci.).

pH >6.5 in hydro/coco: Fe, Mn, and P lockout. The plant can show deficiency symptoms even though the nutrients are sitting in the reservoir.
pH <5.5 in hydro/coco: risk of Fe and Mn toxicity; growth inhibition also begins (Veazie et al. 2025, NC State).
pH >7.5: severe micronutrient deficiencies; iron precipitates almost completely even when chelated with EDTA (only EDDHA chelates hold at this pH).
pH <5.0: clear growth inhibition and cumulative root damage.

What is the actual difference between a mineral acid and an organic acid?

A mineral pH regulator (like the phosphoric or nitric acid in ACID PRO) releases H⁺ ions immediately, stably, and predictably. It drops pH with precision and adds no carbon compounds to the solution. It is the right call for inert systems with no active microbial life, where only solution chemistry matters.

An organic regulator (like ACID BIO, which uses biodegradable organic acids) also releases H⁺ and lowers pH, but the organic acids are metabolized by the substrate's microorganisms instead of accumulating as mineral salts. In soil, every correction with a mineral acid adds salt load; with an organic acid, the correction integrates into the organic matter cycle without leaving accumulated ionic residue.

When should you use ACID PRO vs. ACID BIO?

ACID PRO in hydro and coco: inert systems with no meaningful microbiology in the solution. You need precision — the correction has to be exact, stable, and add no carbon that could feed biofilm in drippers or the reservoir.
ACID BIO in soil: living soil has fungi, bacteria, and fauna that depend on stable pH and organic matter. The organic acids in ACID BIO correct pH without adding mineral salts that the microbiome cannot metabolize.
If you grow in soil and use ACID PRO regularly, every correction adds mineral salts to the substrate. One-off correction is fine, but week after week it can raise substrate EC and inhibit soil biology without showing up on your solution meter.

How do you actually dial in pH in practice?

Mixing order matters: add all nutrient concentrates to water first (SIGMA → CALMAG → ALPHA → BETA → GAMMA), measure the resulting pH, then add the regulator drop by drop while stirring. Not the other way around. If you add the regulator before the nutrients, pH will climb back up when you add the salts and you will end up overcorrecting.

Add the regulator in small drops while agitating. Allow 20–30 seconds for the pH to stabilize before measuring again.
With hard tap water (pH 7.5–8.5, common in many regions), you will almost always need to bring pH down — use ACID PRO or ACID BIO depending on your substrate.
Check EC after adjusting pH: regulators also contribute ions and can shift conductivity.

What is pH rebound and how do you prevent it?

pH rebound is when the solution climbs back up after you have already adjusted it. It happens for three reasons: tap water bicarbonates consume the added acid (residual alkalinity), microbial activity in the rhizosphere produces metabolites that push pH up, or the nutrients themselves — as basic salts — buffer the solution upward. Singh et al. (2019) documented this phenomenon with acidifiers in fertigation systems (J. Hortic. Res. 27(1):31-36).

With very hard water (>300 ppm carbonates): consider a pre-acidification step or diluting with RO water before mixing your solution.
In recirculating hydro: check reservoir pH every 24 hours and correct before it drifts out of range — do not wait until you see it in the plant.
In soil: rebound is slower because the substrate buffer absorbs the swing; a weekly correction is usually enough.

Technical information based on a review of the scientific literature on cultivation. It is not medical advice and does not imply in-house trials of the product.