AquariaWise is a participant in the Amazon Associates program and a few other affiliate programs and may earn from qualifying purchases at no extra cost to you. However, we have vetted every program in this guide and believe they are the best for generating affiliate revenue. You can read our full affiliate disclosure in our privacy notice.
When most people get a new fish tank, they are quite eager to add fish and have them swimming as soon as it is possible. But adding aquatic life into a new aquarium too fast will spell doom for your animals.
The best practice is to give your fish tank a month (four weeks) to six weeks to fully cycle. I recommend adding your fish only when you’re sure there are sufficient beneficial bacteria colonies in your aquarium, and your water parameters are stable.
Essentially, your ammonia and nitrites reading should be (and remain) at zero and the nitrates at 20ppm on the higher side; if you can keep them below 10ppm, that would be best.
A few tricks like using an old filter sponge to help establish beneficial bacteria faster, and ammonia for a fishless cycle instead of using live fish to trigger the process, and adding products like safe start can help hasten the cycling.
Even so, the process is generally lengthy and will most times take a little less or more than four weeks, anyone claiming it is possible to add fish in a new tank within 24 hours is at best overzealous.
Can You Add Fish to a New Tank Right Away
As I’ve mentioned above, it’s not possible to add fish into a new tank right away. You need to wait a while for the beneficial bacteria colonies to establish in your filter, and sufficiently clean the water to keep your animals alive.
You also need to wait for the parameters in your fish tank to become stable, including ammonia, nitrites, nitrates, and the ph.
Of course, the alkalinity or acidity of your aquarium will depend on the fish you plan on keeping.
Most African cichlids prefer alkaline water, while species from the Amazon region, including bristlenose plecos, and tetra like things more on the neutral to the slightly acidic side.
Also note, that hardy fish species like mollies and platies can be added into a new fish tank sooner than you would with more fragile fishes like discus.
Can You Put New Fish in Tank Right Away
When considering a new member to an already existing fish tank, adding them right away or within 24 hours is feasible, just make sure you acclimate them correctly and keep an eye out to make sure other members are not stressing the new guys.
Even so, you do not want to add a fish with parasites or ailment in an aquarium with other animals. Therefore, I recommend adding them to a quarantine tank first, for about three weeks to clear any pathogens on the new additions.
You also want to consider the parameters of your fish tank before adding new fish.
To start with, ensure the fish will fit in your tank when fully grown, plus the water conditions will support its development and live comfortably.
Quite often, fish keeper tend to overlook the impact of temperature, salinity, and water ph when adding new fish, so remember to check your reading are right. Ideally, any fish prefers an ecosystem close to what they are used to in the wild.
Lastly, do some research on companions as not all fish will live with tankmates. Fish like betta, cichlids, and pea puffers are quite challenging, while mollies, platies, and cory catfish are generally more accommodating.
How Long to Wait to Put Fish in Tank After Cleaning
I do not recommend moving your fish while cleaning your fish tank, but sometimes it might be inevitable, like when you have significant algae or snail issue.
In such an instance, I advise giving your fish tank up to 24 hours after cleaning for your parameters to stabilize before putting the fish in. This is especially important because you may need to add new water to your aquarium which the fish are not accustomed to.
You also want to make sure the new water has no chemicals like chlorine, which are known to harm tropical fishes. It’s even better to use RO water if you can access it.
Lastly, before adding your fish back in, make sure you check all parameters to ensure they are within safe limits. Get a test kit like this one whenever you need to take your readings.
How Long to Wait to Put Fish in Tank After Conditioner
This is one question that pops-up in my radar quite often, especially among new fish keepers, which I must say is pretty unclear because you can add most conditioners in your aquarium with the fish in it, there is no need to move them.
As such, you would only need to take precaution, or in this case, delay adding your fish when working on a new fish tank.
Moreover, if you just finished a deep cleaning and conditioned your new water, the usual 24 hours rule (discussed above) will apply.
With that said, its necessary to note that there are two main ways of adding conditioner or clarifier in a fish tank, both of which are pretty common.
You can add it directly to the tank to treat the active volume of your aquarium or add as required for the amount of water changed, either way, your fish should be safe.
Adding Fish to Established Tank
Adding new fish to a fish tank follows an acclimation process, which you need to implement very carefully. However, when keeping freshwater fish only, it should not be too much of a hassle as it usually is with marine fish and corals.
Before adding new fish to an established tank, you first want to check your parameters, make sure everything is right for the fish you have.
Of course, since you already have fish in the tank which are still surviving, we can assume your ammonia and nitrite levels are Ok, though taking the test to be sure won’t hurt.
That said, please make sure your new fish can stand the ph and temperature settings of your existing fish tank because not all aquatic species like the same parameters.
After that, the only thing you need to do is temperature acclimate your fish before adding them into the tank. Basically, the process involves leaving your fish floating in the aquarium while still in the shipping bag for 15 to 30 minutes or till it’s had enough time to accustom to the tank’s warmth.
If you have aggressive fishes in the tank already, you might want to take some precaution as most will try to nip into the bag to get to the new member, which can really stress the new addition.
I also like to turn off the lights when acclimating skittish fish like plecos to make them more comfortable and help them accustom to the fish tank faster.
One last thing I recommend is to quarantine any fish that look sickly first to avoid adding them into your healthy tank while they have an infectious ailment.
In the same light, please do not introduce pet store water into your fish tank because other than the fish, the water might be carrying pathogens that you do not want in your fish tank.
Adding More Fish to An Aquarium
If you need to add more than one new fish to your fish tank, I recommend adding a few of them at a time, then giving your aquarium sometime to settle before adding the next batch.
Personally, I give it a few days to a week, and if the readings (parameters) do not change, then I add the next batch of fish.
Ideally, you don’t want a spike in ammonia and nitrites. Nitrates will most likely change, but it’s is fine as long as they do not go beyond 20ppm.
As you would expect, you will need a spare tank to temporarily hold your extra fishes while you monitor your main aquarium, which is, in fact, better since you can treat that as your new fish quarantine tank.
That’s all, happy 🦐🐠fish keeping.