they eat plants in my tank, their body and stomach is green, thats why.. then all of a sudden they die.. no redness, desease, no nipping from other fish or something..
I don't mean to butt in but I do concern this statement most. Cory is not typically eat plants as far as I know. They do go over the plants looking for little bits of food or micro organism and such. They do require more meaty food to survive. If some of the worm is not available to you. Here is you might be able to get your hands on. I personally never than this but I heard they do enjoy the earthworm. Either small ones or chopped up small enough so it can fit into their mouth. Just you need to make sure the earthworm is came from clean place and not contaminated or poluted. I don't know if there is such a thing at where you live but bait shop may sell them. Then again, you need to ask if they are farmed or collected in wild. Either case you need to know how clean they are.
Also how often and how much are you feeding to your fish? And are they enough food reach to the bottom for your corys? If not, it is good idea to feed some sinking food(you can always soak the flakes with water from the tank they are in, and pour it back after few minutes) after the tank light is out so other fish is less likely to eat them all.
I also worry about the statement of "green body and stomach". Although there are some species more greener than other but I don't think the albino would be green. Unless of course, the horrible dye injected so call "X'mas cory" which were green or red dye injected albino and was around for a while. If you are talking inside of stomech and it's green, I would worry that they are not getting enough food and forced into eating more plants matter.
And how skinny when they die? It sounds like they are starve to their death. Since they are dieing one by one after a month or so. It maybe good idea if you can ask the store/person you aquire these fish from "what are they feeding?" Or bring the dead body to them and ask their opinion also? They may even test your water?
Since you cannot have test kit for water parameter. And you do not have picture of corys. This is just a speculation at best but it sure sounds like your corys are dying from starvation.
i do clean my subtrate.. syphoning(wrong spelling)..
maybe the temperature or other factor? my other fish seems fine except for the male guppy, ithink the pumps flow is to strong 4 my guppy.. help please!!
It is possible but without the what temperature it is, it is impossible to say.
Anyway, good luck. I hope there are no more casualities.