Would a new 500 L marine aquarium need to be cycled again if upgraded from 80 L nearly finished cycling?

Question

I have a 500 L aquarium I would like to fill with saltwater and eventually fish. I have an 80 L tank starting to cycle now on the 3rd week, containing about 2 kg of live rock.

I plan to partially fill the 500 L tank with the contents, filter and power head of the 80 L tank, and over the following weeks, put in newly purchased live rock, more coral substrate, and more water. Week by week, I plan to add more water.

Will this plan have a chance at success, and if not how should I modify it? I don't want to spend all my money at once!

Answer 1

This answer assumes you have a deep sand bed (photos) in your aquarium.

When you cycle your aquarium, it means all your micro-fauna are being built. The lower part of the sand bed should already have some anaerobic bacteria living in it. I'm not sure that it's already built up in 3 weeks, but surely it is on its way.

When you move items to a new aquarium, probably you'll lose some of your bacteria. To prevent having to cycle from the beginning, you could move all that sand very carefully, keeping the bottom sand at the bottom and the superficial sand at the surface. This way you can preserve the majority of your bacteria. Over time, they will recompose, without taking an entire cycling period.

This can be a successful process, but it'll add 1-2 more weeks to the entire process.