The ingredients of these products are not fully known, so it is not possible to determine what they actually do. Based on safety data sheets, it is known that several ”liquid carbon” products use <
glutaraldehyde>. At concentrations below 1% this is used as a powerful disinfectant and biocide and effectively destroys several microorganism, virus, and spores. Above that ratio is becomes <
toxic>. In any case, Glutaraldehyde <
is not a carbon source>, at least in significant amounts, and it <
does not seem to improve plant health>. Glutaraldehyde is effective when applied directly to algae (outside water). However, it is not a selective biocide, so it can possibly damage all organisms inside a tank if dosed directly in the water column at a given concentration. IMO, these liquid carbon products should be used exclusively against algae when there is no other option and not in the water column.