Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
It is better to remove the fish while you are doing that major a change. Here is how I would handle that:
During the week before vacuum the substrate pretty well. Try to get up as much of the debris as you can.
Clean the filter.
If you need to do anything to prepare the water for a water change, do that. Assume a 50% water change, so make sure the GH, KH, TDS are the same as the tank.
The day of the major change:
Turn off, unplug... the equipment.
Put some of the aquarium water in enough buckets to hold all the fish. Aggressive or predatory fish separate, Loaches separate from others, schooling fish together. Put lids on the buckets. About 1 gallon to 1.5 gallons of water in a 5 gallon bucket is fine for most fish.
Remove the plants. (This is a good chance to treat for algae- read more details about possible dips that are safe for plants, but will kill algae)
Drain as much of the water as you can.
Rearrange the substrate, making hills and valleys, use rocks, driftwood.
Plant, misting often.
Put a plate or plastic bag over the substrate and refill the tank, allowing the water to seep slowly over the edge of the plate. This will minimize clouding.
Add the fish, but net them out of the buckets. Fish under stress with produce more than average ammonia, and stress hormones. Do not use this water to refill the tank.
Keep the light off the rest of the day. Feed only if they are behaving normally.
Next day: Test for ammonia, nitrite, nitrate and be ready to do a water change if needed. Lights on, feed normally.