Is My High Turnover The Problem

[farmerhoggers]

Hi all. i have had a problem with 5 of the 10 harlequins i bought 2 weeks ago dieing and wordered if a high turnover/flow rate could be the cause. my water parameters are good although quite hard on the api liquid gh test but seeing as they came from similar water i dont see this as the problem. my tank is 115 litres and is been filtered by an ex1200.  
 
the fish were stocked on a sunday afternoon after gradual water acclimatisation and by mon morning i was down to 9 and the fish was never found. mon night lights out all nine were present. tues morning down to 8 but this time fish was cought on the strainer basket. tues at lights out 8 wed morning 7 but no fish found again! it was at this point i halfed the flow on the filter and i remained at 7 fish for some five days with no probs. after the five days i started to open the flow up again over the coarse of three days an on morning of day four 2 more gone however both were recovered near to the strainer basket.
 
All the fish have appeared healthy with no apparent signs of ill health. is it just a simple case maybe of been dregged to the filter when sleeping maybe at night, do they even sleep? lol help and advice appreciated

 

[hobby5]

Don't think the filter is the problem. It will not matter to a healthy harlequin. Besides they know how to find spots with less current in your tank. And of course a dead fish will be dragged to the filter eventually. As I already wrote in your journal, your fish did not look like healthy harlequins in the first place. They were not high enough and the back was kid of bend round. All signs of malnurishment over quite some time or the presence of some disease. So you most likely bought week/sick fish already.