Base rock is cheaper than LR
. You could add it as you go, though, it doesn't have to be all at once. One rock a week here and there will work. Just don't add dry LR
rock after the cycle is done. It'll need to be base rock or wet, cured LR
that you add after the cycle. The BB should grow in your canister filter in the meantime.
You might have not had a strong cycle with only 20 ppm
of nitrates at the end of the cycle. You'll need to start slowly with fish; add 1 at a time and space them out by 2-3 weeks to give the BB time to catch up.
The canister will be okay, as log as you rinse everything well every week. I have a Fluval 406 on my reef tank and its been fine. But I clean it regularly and only have 2 sponges, chemipure and purigen in it. And Fluval recommends changing the large black sponges every 6 months, but I change them every 2-3 months. And I squeeze/ rinse them well eery week. Those sponges are pretty cheap on amazon.com.