hi, new planted tank, used aqueon shrimp and plant substrate, hardish water( gh, 60)( kh 40)( ph 7.5)( nitrite 0)(, nitrate 15), readings off test strip chart,(api 5 in 1) ammonia level still at about 3.0 any idea how long i should wait for ammonia levels to go down? the planted substrate says will go up but i have done 3- 20% water changes and going down slowly, using co ops sponge filter, medium size in tank