Originally Posted by RuslanJamil

Trace elements = micronutrients = elements needed for plant growth but in extremely small quantities only. Large amounts will normally cause toxicity. There are normally 6 elements in this group: B (Boron), Fe (iron), Cu (copper), Mn (Manganese), Zn (Zinc), Mo (Molybdenum) although some trace mixes have some other elements as well.

Loose ferts are chemicals like KNO3, KH2PO4, K2SO4 where you can control each nutrient somewhat independently from the rest, something that you cannot do with commercial premixed fertilizers.

CSM is one of the many trace element mixes available. Unfortunately, I have never seen it in Malaysia before. It is very popular because the PMDD formula (one of the first DIY fert formulas) uses CSM as the micro component. CSM+B is the trace mix with Boron.

Most of these trace element mixes were meant for conventional argriculture as well as hydroponic farming. They were never meant for aquarium use but all plants have similar requirements so they work!