Found 2 types of Most horrible pest in my tank- need help..

[newlife]

Recently...I notice a major loss of shrimplets...so decided to focus my eyes to check it out. This is what I found which leads to posting this thread at 6.06am.

1st was the horrible Nymph. Dunno from what kinda flies....but luckily they were small. Size like a new born shrimplets with 2 fiddles front & back (sorry...no pix...too small to take) Has seek advise from silane..and was told that small nymph are still quite harmless to the shrimps. I have not been adding plants or driftwood since I set up this tank...wondering how they came into my tank???

2nd was the eye straining Hydra...wondering where the hack they came from??? How harmful are they??? Will The sting kill the shrimps???

Currently, all my shrimps has been move to breeding box...all driftwood and moss have also been removed. Have clear about 10~15 nymph and hopefully there is anymore. Will do a check again before releasing the shrimps back. Is there any fish that eats them up?

As for the hydra...can anyone advise me how to remove them totally and how to prevent them in my tank. Any medication that is harmless to the shrimps??? And how they came into my tank???

Should I pour some boiling water to the driftwood before putting back into the tank???