You mentioned the tanks( SUBTRATE) within the orb is large stone(and you say I siphon ) thats noy easy LOL::: grow a frog instructions are fine until bacteria issues arrive then we have posters : not your fault am so glad asked:: over 1000 previous post worth reading if you care to take time

Make it simple: remove gravel then add external filter which will balance your tank for you:: froggy will be so happy and i guarantee you will never ever post here with issues again: so long as you follow feed clean regime