I made bunch of root tabs with Osmocote the other day following instructions from the forum.
The first time, I placed about 10 capsules on my 46 gallon and water parameters stayed fine. So, I thought it has no impact on water.
Yesterday, I placed about 25 capsules on the same tank; thinking that it would be okay to have higher density.
24 hours later, my ammonia and nitrite both skyrocketed!!! (both over 5 ppm)
Fortunately, no fish or shrimp died. Hope it did not cause any permanent damage to my tetras, guppies, and corydoras.
I performed immediate 50% water change and added Seachem safe to detox the ammonia and nitrite for the time being. I guess I will need to perform daily water change until it stabilize again. sigh...
Lessons learned. Be careful with DIY Root tabs!!! Your filter maybe able to handle some ammonia released from the Osmocote, but its capacity will vary!!!