Could it be the plants starts to leak sugar at the snail damage and the algae gets a hold and the entire plant eventually weakens?
They seem to be most frequent close to the substrate on the lower leaves. Though some seem to munch a bit higher up as well.
They could be responsible for some weakening. MTS stay in the substrate during the day but invade the land of the living during the night. Sometimes you can see them on the glass at the top of the aquarium. Snails rasp the surfaces picking up bacteria, algae or plants. Most snails we keep in our aquariums are not powerful enough to eat plant leaves. However some plants are very delicate ( H. pinnatifida is not one of them ), and some have brittle leaves from deficiencies. Maybe if a snail concentrates long enough in one spot it can create some damage. Brittle nose are another issue, better keep them fed
I don’t think the spots on the H pinnatifida are the results of snail damage, but I do not know firsthand what causes them. I have this plant in my aquariums, I will try to induce/cure these spots when I have some time to set up a real experiment. I’ll let you know when I have something to show, instead of just coming up with fascinating dreamlike explanations like others.
Clea helena is the black ops when it comes to snail killing. You should be able to find some at hobbyists or pet shops, you will only see shells …
The method you have outlined, that while it might produce a more accurate result in a lab, is not something that should be done at home by an untrained individual without precise instrumentation. You have turned a two step process into an human error inducing nightmare. How many times do you want him to use a 100 mL graduated cylinder (provided he even has one, and knows how to measure accurately with it) to split up stock solution, and measure / split fresh water? Looking over your methods, there are FAR to many times a layman could make an error...perhaps even bigger than the 3% your trying to fix.
I have to confess, that the method I described is standard operating procedure in the lab, even for training students. You know why, because it is easy to do, provides accurate and precise results time and time again and it does not require expensive/specialized equipment. It is used exactly to reduce error. Lab humans are just as prone to error as “the layman”, this is why we use the serial dilution. If we were not susceptible to errors we would dose exactly 1µl. Many newbie students and experiments show that it is not as you describe it.
Serial dilution is something so easy that it is taught in high school here in the EU in the chemistry class, not an advance lab technique. I would say measuring 10ml requires less precise instrumentation than measuring 51.72ml, wouldn’t you ? 52g or 1g ? I respect the OP enough not to insult his skill in measuring 10ml. Notice I picked 10ml not 1ml precisely to make it easier to accurately measure. Don’t feel confident ? do it with 100ml. Made and error ? there is plenty of stock solution to retry.
I bet you were laughing when you insisted someone use 52 grams of lab grade KNO3 in your solution?
Don’t get the joke… KNO3 is cheap here. Besides you can use the rest of your solution as part of EI. I would not do the same with 5l of PCR primer
He wants to know if he has 20,25,30 ppm of K; not 23.1 or 22.5 ppm. Unless you are trying to teach the OP fundamentals of laboratory measurements, I suggest you stick with the best way to do something, nt the proper.
A reference solution is a reference solution no matter where you do it and what your aim is. It should provide an exact, known concentration of a solute, ie a 20ppm K ref. sol. Should have 20ppm K. Knowingly introducing errors is not part of the process of creating a reference solution. A solution that has 20-23ppm K is not a reference solution.