Ostracods killing my fish?

HI so I got four new platies on May 30, 2016 and added them to my 36 gallon tank that had a red tail black variatus and a zebra nerite snail in it. I have not done a water change since May 21,2016 and plan to tomorrow or this weekend. Yes I do know that I need to change the water more. So I noticed on June 3 that there were little brownish dots moving around my tank and realized that they were alive! After doing some research and posting on another forum because I thought they were daphnia at first and wanted answers as to how they got there, someone mentioned they looked like Ostracods. Indeed I have determined they are. They only showed up, well I only ever noticed them, right after my new fish came into the tank. But now two have died. One on June 6 and one on June 9. I have read somewhere that the Ostracods can kill your fish sometimes. I'm wondering if that's this case or is it just new tank syndrome and me inadequate water. The two that died acted odd from the outset. The other two left are eating like pigs and seem perfect. How do Ostracods get in my tank and how to get rid of them and are they killing my fish! thank you for your help it is much appreciated

 

There are wide variety if that's what they are,
though its more likely that the platies are killing them.

id need some watertesting to know if the water quality is to blame.

 

We can't really rule anything out unless we know water parameters and how you acclimated the fish.

 

I breed guppies and have the same suspicion about the appearance of ostracods and the expiration of fishes.

After finding out what these creatures were and doing a little research I came to the conclusion that they can possibly be harmful to fish :
1. If they bloom in your tank and there isn't enough waste food for them and their young to eat that they begin to feed on the fish.
2. That their "blooming" appearance in large numbers heralds a change in the water that may become toxic for the fish in some way, like bacteria bloom or oxygen depletion etc.

found on-

I've just found 3 things in my tank that resemble little seeds I got them out with a cotton bud and squashed them and it broke into two, I googled what they could be and seed shrimp came up, never heard of them before, are they harmless? Is it a coincidence that 2 of my Guppies have died in the past few days then I find these?.Btw the ones I found are darker than these ones.

ostracods prefer to eat unicellular bacteria and algae. some species have been observed eating away at soft bodied animals and almost all species will readily consume decaying matter. usually a boom in ostracod population would mean their food source (either bacteria, algae, or something dead in the water) is abundant. it is the sudden spike in population of bacteria that is a threat, because 1) it means nitrogen is readily available for specific bacteria in the form of , nitrite. and 2) some bacteria require oxygen to exist and they make dissolved oxygen in the water less available to other high-oxygen demanding species like fish.usually, sudden spike in ostracod population is an indicator that some sort of unicellular organism is thriving in your tank, and that unicellular organism is another indicator that some nutrient (be it ammonia, nitrates, nitrites, carbon dioxide, etc. remember, many different types of bacteria exist that relies on a specific chemical food source) or another has also suddenly become available, which may harm your fish.

 

If you read that last paragraph, from Isaac Park, you will see that the Ostracods, or seed shrimp, are not the cause of the fish deaths, but they are a symptom of the poor tank conditions that are probably causing them. They only thrive in tanks with a lot of detritus, which usually contributes to high ammonia levels and bacteria blooms. Add a lack of water changes, and BOOM! - population explosion.

 

If you read that last paragraph, from Isaac Park, you will see that the Ostracods, or seed shrimp, are not the cause of the fish deaths, but they are a symptom of the poor tank conditions that are probably causing them. They only thrive in tanks with a lot of detritus, which usually contributes to high ammonia levels and bacteria blooms. Add a lack of water changes, and BOOM! - population explosion.

Yes I said that in my second point, and also in the first and second line of what Isaac Park said is "some species have been observed eating away at soft bodied animals"
This is how I made the "assumption" that it is possible that if there was a Ostrapod population BOOM that they could possibly attack the soft parts of a fish, possibly Gills or the female sexual parts or anal.
This is Obviousley only my Assumption, I'm not that tiny or have the visual equipment to verify that. Either way for someone without any fancy water testing equipment they are a good indicator for me that the water isn't at the quality that I would like it to be for my fish.