Root tabs safe for corys?
Apologies for the newbie question. I'm pretty new to planted tanks.
My 30g is about 2 months old and moderately planted, low tech. Substrate is black sand ('Limpopo'). Hard water but other parameters good (Nitrates 20ppm, no nitrites or ammonia). Standard 2x fluroescent tubes. Temp 26. Stocked with rhombo barbs, false julli corys, a bristle nose pleco and a small angelfish.
My amazonian sword had been doing very well, growing new green leaves and thriving. Over the last fortnight several leaves (both old and new growth) have started to die from the tips, initally going brown then clear/grey as the death spreads. Lots of roots poking up all over the tank so I assume this is an nutrient issue as sand is not going to cut it. Have been adding seachem flourish for trace elements for last fortnight but new leaves keep dying. The healthy leaves also look a bit less green than they did. It seems to me that I need some root tabs but I'm concerned that my cories could dig them up and I don't know if that would be dangerous. API root tabs seem the cheapest option and I've ordered some on Amazon but there is no ingredient list which worries me (hopefully trace elements and iron only).