hello; I don't know what the snails are from the description. You might do a search for freshwater snails( trumpet, ramshorn are two common to aquaria) I sort of gathered that you think the snails were introduced with the daphnia. It is possible. Snails can also be introduced with live plants and stuff purchased from fish stores. When gathering things from ponds you can pick up extras, such as parasites. (while it is very unlikely in your case, there are some human parasites that spend a protion of their life cycle in snails. I do not think this occurs in the U.S. Of course I do not know where you live. Could be anywhere on the globe.)
I have kept a quarantine tank for many years now. I keep anything new it for an extended period. (some on this forum suggest a minimum of 4 weeks and that makes sense to me.)
The daphnia are also called water fleas and I have collected them as fish food. If you read some of the betta posts you will find that they are not always easy to feed. I find much truth in these posts and it mirrors my own experience. One additional thought is that bettas do not always understand what is food right away. I used to keep wingless fruit flies for surface feeders and my bettas might ignore them for some time. Once they understood that they were food, they sought them out. The betta may catch on that food is swimming around. I have tried to culture daphnia with no success. I doubt that they will cause any problem. You have a desireable live food it would appear.
If the snails turn out to be the type common to aquaria, then they will be ok as well.
About what you should do. It may be that that you are ok. If you have introduced something bad, it will show up eventually and you can post a particular description of the problem. If you have other tanks, it may be best to not use any material or equipment from this tank untill you are sure.
I prefer to have snails in a tank. I have the trumpet snails and red rams horn snails in all my tanks. They do eat algae and any uneaten bits of food. If the snail population gets too large, I keep a set of needle nosed plires handy. I pluck them out, crush them with the plires and feed them to the fish.
I think I might want to give you a little background about how it all started. So I was out fishing on the Mississippi, and I kept realing in a bunch of valls, so I thought, cool, free plants! I took them home in a little water bottle and rinsed them off very well. I filled up a little 5 gallon plexyglass Critter Keeper with a screened top and put in some sand and a lamp overtop.
Over a period of 3 or 4 weeks, the plant started to take off. I did not notice any water insects besides one little limpet snail which I thought was pretty cool, so I let it stay in there. The water sat for about 2 more weeks before I noticed a few daphnia. This makes a total of about 6 weeks before any daphnia were noticed, and considering they have been enclosed in a healthy environment for all this time, I would assume they are parasite free. Just to be safe, I let them sit and breed for a few more weeks before I netted out 4 or 5 and tried to feed them to both of my tanks. This is when they were left to breed underneath the gravel and now are everywhere.
It is more noticeable in the fifteen gallon which houses 2 platys (female), Red Cherry Shrimp, 3 Endlers (2 female 1 male) and 2 peppered corys. As you can see in my signature, it is highly planted. I am more more worried about the daphnia devouring my plants, which is not to say I don't care about my livestock, I love them! But if limpets can do damage, I guess that will also add to my worries. I'm assuming the limpets were transfered while still eggs when I breifly introduces a mysterious najas grass looking plant that was also in the 5 gallon quarentine.
So even if they are not harmful, do you know how I would rid of them? Even if it involves removing my invertibrates for a while?
Thanks SOOOOOO much for your help, a am at ease knowing that nothing to damaging will happen right away. And yes, your a hero too skjl47!