Regime
PMDD
Philosophy
PMDD (Poor Man's Dupla Drops) is a historical milestone in DIY aquatic fertilization, created in the mid-1990s by the online hobbyist community to demystify expensive commercial products. The original philosophy is built on two core pillars: extreme cost efficiency and absolute control over ingredients by mixing dry chemical salts (KNO3, K2SO4, MgSO4, CSM+B).
Scientifically, PMDD was formulated around the theory (now partially outdated but historically significant) that phosphorus was the primary trigger for algae blooms. Consequently, the original formula strictly limited phosphorus in the water column (targeting near-zero PO4) to force plants to consume nitrogen and potassium rapidly, thereby starving algae. While modern aquascaping recognizes that severe phosphorus limitation can stunt plant growth and trigger certain algae, PMDD remains highly popular for multi-tank systems, providing unmatched mixing flexibility and cost savings.
Recommended nutrient targets
| Parameter | mg/L |
|---|---|
| N (NO₃) | 15 |
| P (PO₄) | 1.5 |
| K | 25 |
| Fe | 0.3 |
| Mg | 4 |
| Ca | 15 |
| B | 0.015 |
| Mn | 0.3 |
| Zn | 0.02 |
| Cu | 0.008 |
| Mo | 0.002 |
Dosing frequency
Daily (diluted stock solutions)
Water change
30-50% weekly
CO2
Pressurized recommended
Light
Medium-high (40-70 PAR)
Pros
- Extremely affordable
- Full control over composition
- Flexible and scalable
- Active DIY community
Cons
- Requires initial preparation
- Precision scale needed
- Not for simplicity seekers
- Dry salts to source
Common Errors
- •Weighing dry salts poorly with generic kitchen scales (use a 0.01g precision scale).
- •Mixing macro and micro solutions in the same bottle without adjusting pH, causing precipitation.
Advanced Techniques
- •Modifying the Nitrogen/Phosphorus ratio seasonally or based on the type of algae appearing in the tank (e.g., increasing PO4 to combat GSA).
Ideal for
DIY hobbyists wanting savings and full control, especially with multiple tanks.
