TDS levels come from everything you put into the tank, ie. food, fertilizer, minerals leached out of rocks and other hardscape, even chemicals like excel and prime etc... so overtime, TDS will always be constantly increasing in a tank.
Regular water changes with lower TDS water is the only way to keep it low. Reducing feeding and less fertilizer dosing helps slow down TDS rising too, but for planted tanks, fertilizer dosing is a necessity for maintaining good plant growth anyways, so can't reduce that as much. Compounds that contribute to TDS levels will stay in the water until removed.
Fishes and shrimps that come from low TDS/softwater environments are used to very low mineral and nutrient content in their natural waters (their aquatic environment is usually almost devoid of plants), which is quite different from our planted tanks with all the rich assortment of nutrients being dosed regularly in order to grow lots of plants. Fortunately, most of fishes and shrimps we keep can adapt to higher TDS/harder water, so it just a matter of gradual transition and acclimation.
You do have to be careful when doing large water changes to reduce TDS though, especially if the TDS was a much higher level. The livestock may have already been acclimatized to the higher TDS conditions, so if the drop is too sudden and too much, their osmotic regulation could be thrown out of balance and cause issues. Especially for shrimps which maintain their shells according to water conditions, they can't adapt as fast as fishes, hence changes in TDS affects them much more... it's one of the reasons why water changes tend to trigger molting in shrimps (using an analogy, its sort of like them having to change clothes).
Bookmarks