“Bugs” in my tank!!!! HELP!!!!

Hello guys, I’m a little confused as to what this “bug” is and if I can get rid of it. I’ve had a 3.5 gallon tank with filter and heater for a betta fish with a mystery snail. I’ve had the tank up and running since October 2020 and have had no issues until recently. I went to introduce a new snail about a month or so ago and it didn’t look too hot when I got it so I figured it wasn’t going to last too long. Around the time it died I started noticing these small bugs. They would just float around and would be in my filter. So I would empty the filter to make sure they wouldn’t be in my tank. I did have three small moss balls in my tank but after noticing some debris or even egg looking stuff on the moss balls I decided to take them out and throw them away. After asking someone at petsmart what they could be and then telling me they have no idea I come to you guys. I’ve cleaned my tank down to literally a 90% water change as well as changed the filters and gravel and they are still there. My betta is slowly dying since I’ve gotten these things. Please help!!!!! *** the attached pictures are ones I’ve scooped out of my filter and are “dead. They seem to be clear when they are alive and in the water.

@Adc - one I think I can answer ?

I think they are known as bladder snails...I had two at one time and now they are everywhere!!

I’m not sure if they are floating round though...?...perhaps best to await an answer from a more experienced member..? ?

My first thought on looking at the photos was bladder snails as well, but the description of their behaviour doesn't fit as they usually crawl on things rather than float

the ones that look like they have a shell could be ostracods (harmless and beneficial).
The wormy things in the moss ball are either worms or leeches, again nothing major to worry about as they occur in most tanks

NannaLou said:

I’m not sure if they are floating round though...?...perhaps best to await an answer from a more experienced member..? ?

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Essjay said:

My first thought on looking at the photos was bladder snails as well, but the description of their behaviour doesn't fit as they usually crawl on things rather than float

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in my experience, my snails like to float occasionally, hence the name bladder snail. they go up and clean stuff if you have floaters or just want to have some "fun".
(they arent very useful cleaners tho ;/)

Colin_T said:

the ones that look like they have a shell could be ostracods (harmless and beneficial).
The wormy things in the moss ball are either worms or leeches, again nothing major to worry about as they occur in most tanks

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After looking at the other comments I am pretty sure after doing some research that they are some species of ostracods. Could they have any type of effect on my betta fish? He is pretty much dying. Stays floating at the top of my tank sideways and very shallow breathing. It also looks like one of their eggs sacs is on his back fin. Could they cause him to do this or would it be something else? My snail seems to be doing perfectly fine.