PMDD Poor Man’s Dupla Drops
is an aqua fertiliser created by two Canadians: Paul L. Sears and Kevin C. Conlin in 1995. They worked on the composition for many years and conducted experiments in their planted aquariums; they managed to figure out the composition of this mix which gives great results. Below are provided the components of the mix:
K – potassium, Mg – magnesium, S – sulfur, B – boron, Cu – copper, Fe – iron, Mn – manganese, Mo – molybdenum, Zn – zinc, E202, E300
Dissolve the content of the ready mix sachet in 500ml RO water. Shake the solution before using. Keep in dry and dark place in room temperature..
2ml of the solution per 100 L tank water a day. In case of any deficiencies, increase the dose so that the maximum Fe does not exceed 0,4 ppm.
This method requires dosing every day so that the level of all of the components is stable and to prevent from deficiencies of any of the components. The fertiliser should be given always at the same time of day, preferably just before turning on the light.
The dosing also largely depends on:
- The amount of plants (the percentage of tank surface they cover)
- Type of plants (how they absorb nutrients – through the roots or leaves)
- The light level
- CO2 level (if it is high you will need nitrogen and phosphorus)
In case of this method, there are no strict rules when it comes to partial water changes – some users suggest changing about 30-50% of water once every 2 weeks. When it comes to additional CO2 dosing, its level in the aquarium should be stable, but not greater than 20 ppm (20mg/L). In case of a higher than that level, you should also dose nitrogen and phosphorus.
It may take a while before you figure out the best dose for your aquarium and your plants, but the end product – healthy and beautiful plants -is worth this sacrifice. The condition of your plants, their growth speed (slow – too little fertiliser), appearance of algae (too much fertiliser), chlorosis on leaves (too little fertiliser) will always be the best indicator whether your dosing level is appropriate.
The PMDD method has proved to be successful in aquariums with too many fish, with few plants (about 40% of the aquarium surface) or with little light.
Before using the fertiliser, check the level of NO3 in your aquarium. If the level is 3-5 ppm then you can add KNO3 to the fertiliser mix. If the level is below 0.3 ppm then you can add more or use a different fertiliser containing KNO3. This is particularly important for aquariums with many plants and with only few fish as in such cases all products of fish metabolism are absorbed right away by the plants leading to possible deficiencies of nitrogen which, as we know, is also required for a healthy growth of plants and is responsible for proteins and amino acids synthesis. It’s worth to mention here that plants contain 500 more of nitrogen than of iron.