ok to start off i have 125 gal 2 year old tank with pfs and a fx5 for filtration. my lifestock currently is two 5 year old florida gar, and two blue crawfish. my water parameters have all been in check , the water is clear and does not smell. but my problem is it seems like everything i put in there dies like the get sick. yesterday i dumped 25 feeders and within 1 hour all were dead but two. the gar and crawfish act like nothing is wrong. really never looked better. i had three adult plecs that went belly up over a two or three day period this summer. is there something im not testing for ? why does everything seem to die in such a short time in this tank but not bother the gar? im thinking of moving my gar out to an outside pond and putting some catfish in it but i dont want to send them to an early death. any ideas?