I recently bought a second aquarium and set it up. When doing so, I added some gravel and artificial plants from my first aquarium to it because a staff member at the store told me it would help with cycling.

I want to make sure that there are no parasites in the second aquarium because a couple days later, I realized some fish in my first tank started to act weird and I am now treating it for parasites.

If I empty the second tank, rinse everything with hot water and let it dry, will it kill any parasites that could have been added to the second tank when I added the gravel and plants?

  • 1
    Do you have any indication there were actual parasites in there or what type? Secondly, a tank cycle takes about 4 weeks and fake plants or gravel or even real plants won't speed it up. You shouldn't bring fish home without a fully cycled tank. If the fish store instructed you to do this with a new tank, i strongly suggest finding a new fish store because you're getting bad information that's going to kill fish and waste your time treating for a problem that doesn't exist.
    – Jestep
    Jan 19, 2017 at 4:35
  • I believe it to be velvet due to loss of color and appetite, fin clamping, and erratic behavior. And there are no fish in the new tank yet.
    – Kate
    Jan 19, 2017 at 5:29

3 Answers 3


I think most misunderstood your question.

Is my understanding correct that:

  • you are currently cycling your new tank, without any fish?
  • you've moved gravel & plants from your existing tank to your new one (to speed up cycling)?
  • you now think there are parasites in your existing tank (not the new one)?

Then the question remains: why do you think there are suddenly parasites in your existing tank? Besides removed gravel & plants, you did not change anything...

So I don't think you're having parasites... There might be 2 other things going one:

  • If you removed too many plants, the chemical composition of the water might have changed. Less oxygen, higher CO2 (also affect pH), higher nitrates, etc. If this is a sudden change, your fish might become stressed & need time to adjust. Only proper way to check this is by testing the water. Fish stores can do that, but they usually do that with these paper strips that are very inaccurate. It's better if you use a testing kit with liquids.

  • Secondly, how much gravel did you remove, and how careful did you do that? Besides your filter, the gravel is also a source of 'good' bacteria that lets you keep stable water parameters. If you removed a lot, it's possible that the current bacteria population is not capable (for now) to keep the parameters stable. Also, gravel can contains a lot of debris from leftover food and dead plants, it can also contain gas from decomposition of it. If you stir up the gravel, these gasses are released in the water. Usually this results in an ammonia spike. And I think this is actually what happened.

For both things, the only way to make sure is to test your water. There are chemicals available to decrease the levels of ammonia (but test first before using them!). Meanwhile, I would suggest that you do a partial water change every day (30% or so) and don't overfeed your fish.

  • Yes, this is exactly what I meant.... "Is my understanding correct that: you are currently cycling your new tank, without any fish? You moved gravel & plants from your existing tank to your new one (to speed up cycling)? You now think there are parasites in your existing tank (not the new one)?"
    – Kate
    Jan 19, 2017 at 18:53
  • And I did not move very much of either, maybe a handful or two of gravel (and I have small hands), because I also bought gravel for the new tank.
    – Kate
    Jan 19, 2017 at 18:56

For a new aquarium, you need to let it empty (just water, gravels and plants) for 4 weeks before putting fish in it. Otherwise, your water will be full of ammonia and other bad things for your living friends.

So taking elements from your first aquarium won't help at all, but as those bad things are in water, you can take some water from your first aquarium to help bring in the good bacteria.

I don't know if it's done a lot in others countries, but here in France you can then take some of the water in your aquarium and get it analyzed by a pet store selling fish and they will tell you if your water is good enough for fish.

So if you already bought your fish without letting the aquarium empty at first, I would advise you to transfer them in the first one if they can live with your other fish, or to take enough water from the first tank for them to live in for some time. Then you would be able to go to some pet stores selling bacteria for aquarium and let your second tank empty for 3 or 4 week, just adding the new bacteria.


What Ise said is partially true, moving decoration, plant and substrate from the first tank to the second will help with cycling, but most of the beneficial bacteria live in the filter. The best way would be to move some of your old media from the first tank's filter to the second tank's. This is not always an option depending on the media, the filter type, etc. A good way to quick start your new tank is to rinse the old filter media in tank water (from a water change) and than dump all the gunk in the new filter. That gunk will contain a lot of bacteria from the first filter, but will still be much better than nothing as of now.

For the rest her answer is pretty spot on, the main problem seem to be that your tank hasn't cycled yet and this is the reason for the fish acting weird.

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