Its not that ammonia depletes oxygen, but the nitrogen cycle uses some oxygen to turn ammonia into nitrate, but not enough to deplete oxygen to a noticable degree. The other link between ammonia and oxygen is that too much ammonia will burn fishes gills so they dont work as well and fish cant then extract O2
from the water properly. But it would take much higher ammonia levels than you are seeing to do this.
Unless you've had much higher levels of ammonia in your tank than the low levels you are reporting, ammonia isnt a health for your fish. Its obviously possible though that ammonia spiked much higher than what your testing is showing now though. Did you see any sypmtoms of ammonia poisoning?
- Red or bleeding gills.
- Changes in the fishes colouration including red streaks.
- Gasping at the surface for air.
- Damaged fins.
- Lethargic swimming at the bottom.
While seeing ammonia at the level you are seeing is not an immediate concern and not a significant health risk, it is a sign your tank isnt cycling out waste properly.
If your tanks filter causes surface agitation i wouldnt worry about O2
. Plants will help with oxygenation if you dont want to add an airstone. Dropping the water level slightly should cause more surface agitation from your filter. Water changes are great for adding O2
short term too.
Before you started your daily water changes, what was a normal water change schedule? Do you see an improvement in your fish now you are changing plenty of water? Do you know your water hardness? If not specifically, do you know if you live in an area with hard or soft water?
Plant melt is perfectly normal when new plants are introduced to an aquarium. They will have been cultivated above water with ready access to CO2
from the atmosphere. You put the plant under water, CO2
is largely cut off, and the plant needs to adapt to its new environment and the original growth may die off or melt. New growth is more tolerant of its new environment with a different leaf structure able to extract CO2
from the water. Old growth die off will add some ammonia into the water, and could explain what you are seeing in your test, but doesn't explain why your fish died. If you see significant plant melt, remove the dying growth. This will stop it contributing to poor water quality and the plant can concentrate its resources on new healthy growth rather than trying to heal poor, unhealthy growth.