FoxFarm Bush Doctor Cal-Mag – Gallon

FoxFarm Bush Doctor Cal-Mag is a liquid calcium and magnesium supplement formulated to correct and prevent common nutrient deficiencies that lead to blossom end rot and leaf tip burn. With an NPK of 1-0-0 and a guaranteed analysis of 3% calcium and 0.9% magnesium, it is designed for use across vegetables, fruits, and herbs. OMRI Listed and CDFA Registered, it is approved for certified organic production.

Bush Doctor Cal-Mag Specifications

Verified values are drawn from the product label and canonical product data. Weight reflects shipped product including packaging.

Why Choose Bush Doctor Cal-Mag

Calcium and magnesium deficiencies are among the most common and damaging problems in fruiting crops, particularly in coco coir, rockwool, and heavily-fertilized soil grows where uptake can be restricted by competing ions or low media pH. Bush Doctor Cal-Mag addresses this directly with a straightforward liquid concentrate that is easy to measure and mix into any feeding program.

• Targets the root cause of blossom end rot and tip burn. Both conditions often trace back to inadequate calcium delivery. The 3% calcium level in this formula supports firm cell walls in developing fruit tissue, reducing the risk of these costly losses.
• Magnesium for chlorophyll function. The 0.9% magnesium content supports chlorophyll synthesis, which matters most during rapid vegetative growth and through the flowering transition when photosynthetic demand is high.
• OMRI Listed and CDFA Registered. Growers operating under certified organic programs can use this supplement without risking certification. Both the OMRI and CDFA designations are independently verified.
• Gallon size suits regular supplemental use. At one gallon, this is the format for growers who use Cal-Mag as an ongoing part of their nutrient regimen rather than an occasional correction. It reduces per-dose cost compared to quart sizes.
• Low nitrogen carrier. The 1-0-0 NPK means the nitrogen contribution per dose is minimal, giving you flexibility to use it across vegetative and flowering stages without meaningfully altering your base nitrogen levels.

Best Uses for Bush Doctor Cal-Mag

This supplement is most useful in situations where calcium or magnesium uptake is likely to be restricted or where the base nutrient solution is light on these secondary macros.

• Coco coir growing. Coco is notorious for holding calcium and releasing potassium, creating a Ca-Mg deficit that requires supplementation from the first feed. Bush Doctor Cal-Mag is a direct fit for this application.
• RO or soft water systems. Growers using reverse osmosis or naturally soft water start with a near-zero mineral baseline. A Cal-Mag supplement provides the background secondary minerals that would otherwise be missing before base nutrients are added.
• Fruiting vegetable crops. Tomatoes, peppers, and cucumbers are especially prone to blossom end rot from calcium stress during rapid fruit set. Supplementing with this product during the early flowering and fruiting window reduces that risk.
• Correcting visible deficiency symptoms. If tip burn, interveinal leaf yellowing, or soft spots on developing fruit are already visible, a Cal-Mag supplement can help stop progression while the underlying cause is addressed.
• Pairing with complex base nutrient programs. Some multi-part nutrient systems are intentionally light on calcium to prevent precipitation in concentrated form. Bush Doctor Cal-Mag fills that gap cleanly without disrupting the program’s NPK ratios. Growers building out their additive program may also find Earth Juice Hi-Brix Molasses or Advanced Nutrients Tarantula useful alongside this supplement for soil-based and microbially-active systems.

Dosing Guidelines

The canonical product data does not publish a specific dose rate per gallon for this formulation. The following guidance reflects standard Cal-Mag supplementation practice for liquid concentrates with this analysis. Always verify against the product label before use.

• Preventive use: Add Cal-Mag to the reservoir or feeding solution before mixing in base nutrients. This ensures calcium and magnesium are in solution before pH adjustment.
• Mixing order: Add Cal-Mag to water first, then introduce base nutrients, then pH up/down as needed. Adding Cal-Mag after concentrated nutrients can cause precipitation.
• EC and pH target: For most fruiting crops in hydro or coco, maintain solution pH at 5.8–6.2. Magnesium uptake drops sharply below 5.5.
• Monitoring: Check runoff or drain-to-waste solution EC weekly. If EC is climbing without corresponding plant uptake, reduce all supplemental feeds proportionally before reducing Cal-Mag specifically, as Ca-Mg deficiency symptoms take time to appear.
• Shake before use: Liquid concentrates can settle. Shake or stir the jug before measuring each dose.

Sources & Further Reading