01 The Victorians Laceplants and potatoes The Victorian gentleman's parlor was awash in cane and bamboo, wood, glass and iron, and lace plants although more often they were grow outdoors "as potatoes but in some water in a shallow bowl". Manure was used for these prodigious feeders. 02 Innes "Dangerous and foolhardy" By the end of the Nineteenth century and beginning of the twentieth the golden age or as Klee refers to it as the "fourth phase" of the aquaria. Mostly recognizable today but with less plants. Innes made a point of stating that aquarium fertilization was "dangerous and foolhardy" although many mysteries existed with the plants he wrote about by his own admission. State of the art in the day was sheep manure tea administered with a burette under the gravel. 03 The 1960s Not much. Potassium chloride. 04 Dupla Towards the optumum aquarium In the late 1970s two Germans made an extensive chemical analysis of the water where Cryptocorynes grow in various parts of Asia and came to the realization these plants are in water with very different water chemistry that one is normally used to. Iron is very very high in native waters. Dupla fertilizers, as part of their system, were not cheap and a bit of a mystery. Horst & Kippers magnum opus - _The Optimim_Aquaria_ was a milestone introducing not only rational aquarium fertilization, but the ubiquitous use of Co2 and high lighting.

05 PMDD Crowdsourced recipe for Dupla drops In the mid 1980s after Dupla has been in America a few years the Internet began tropical fish fora and a formula to replace the pricey Dupla products was crowd sourced and became knows by the abbreviation "PMDD" for "Poor Man's Dupla Drops" 06 EI Tom Barr's "estimative index" approach. 07 Formulas Chemical formulas and recipes