Have recently got an Eheim Professional 2028, 50 gallon tank. Lost s few fish yet water seems to be flowing fast, ther eis an indicator on it but I am not sure how it works, its ared nodule inside that moves, can't work out from the manual whether you should be seeing any of the red nodule if its on full flow. Also if the water is going up intake strainer and coming out spraybar is it working correctly, there is some gunk inside filter so am assuming its working correctly, is very stressful to lsoe some fish, just got back to hobby after 8 years away and kept loads of fish before and never had dissease losses, am worried that its new tank syndrome although filter had some time to mature, what you all think?