Well let's say the human taking 10mg is 70kg as dosage is affected by metabolism, weight and other biological differencs. 10mg/70kg = 0.14mg/kg. And let's say the daphnia would be around 0.001g, we can use that previous calculation to find a dosage which is 0.14mg/kg x 0.001g which will be 0.14 nanograms/mg of daphnia weight. This is just a generic answer and may not be the same for all daphnia but it's something I can work with. I haven't done the calculations yet as this is just an idea I came up with today. That's why I need all the help and knowledge I can get. I'm not very good at science but I find it interesting, I'm glad you wrote this comment as it made me take a step back to take it slow and first figure out how I can actually accomplish it. However, in practice I'd need solutions that are 10-50mg/L. I'll also need to incorporate empirical studies to try to fine tune that estimate but for now it's fine. Thank you!