I suspect there is no straight forward answer to this question but I am seeing some Ammonia build up in a small 45 gallon 1:1 system that's been running tree months. At what level of Ammonia do I need to be concerned for fish health? I have 7 koi 2" to 5", which appear pretty tolerant of water chemistry but they are more expensive than godfish so I don't want to kill them with high Ammonia levels…