thanks mate . ammonia shouldnt be an issue with the aquasoil really , as it had been in the tank for about 5 weeks with twice weekly waterchanges , and a filter seeded with mature media before i planted it , so i would have expected the leeching to be done with by now , although to be fair i have no experience regarding this, so i could well be wrong . flow at substrate level is good and strong , plenty of co2 bubbles getting down there too . perhaps the flow was too strong , lifting the hc and it couldnt root properly ? either way i figured that the best thing to do would be to remove it rather than leave it in and risk triggering algae problems.