Did I kill off my bioload??

[WaterBaby]

I just finished medicating my tank (6 Gallon Eclipse system with biofilter) with tetracycline. I did as the directions recommended: One capsule, 24hrs later another capsule, 24 hrs later 25% water change and another capsule, 24hrs later the last capsule. The manufacturer said that it would not affect the bioload.

24 hrs later, I did a 30%water change and replaced the filter pack using extra carbon to get rid of the meds.

I just tested the water, and have:
no ammonia
no nitrites
pH 7.0

These were actually the values before and after adding the medication

BUT:

Now I have NO Nitrates also. Before I added the tetracycline, I had between 10-20ppm of nitrates, and now have 0ppm. Is this conclusive of killing off all the biological stuff in the tank???

I know most of you would say- great values--- but I was just wondering if the tetracycline actually could have killed off the bioload?

[goldfish freak]

The reason for zero nitrate could be due to the recent water changes. If you only do a water change once a week and have that level of nitrate then the increase of water changes in the last few days may have brought your levels down to zero.
Keep checking your ammonia and nitrite daily for a few days to see if indeed your cycle has been affected. If it has been, then ammonia or nitrite should show up.

[RTR]

BTW, just for clarification, the "bioload" is all the living things in your tank, the fish, the bacteria, the algae, the inusoria, etc. Together they make up the bioload. Their nitrogen waste products are what you measure by ammonia, nitrite, and nitrate. But the bioload is the producers, not the waste.

[WaterBaby]

Thanks for the clarification RTR. I should have said all that good stuff (bacteria) in the biofilter.

[Sumpin'fishy]

I agree. I believe the 0 nitrates is due to frequent water changes. Give it time to settle a bit, and maybe test the water twice during the following week to make sure there is no ammonia or nitrite present.

[WaterBaby]

Tested again.. No Ammonia, no Nitrites, pH 7.0 and Nitrates back up between 10-20ppm. Whew!

Must have been the water changes.:)