# How many fish to add at once?



## oscarsx (Mar 15, 2011)

Is the cycle complete? If so, you can add as many as you want.. just make sure you know your limits... how long has it been up and running? 

and what type of fish are you planning on buying?


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## xenxes (Dec 22, 2011)

I wouldn't add as many as you want lol, every livestock added increases the bioload and your tank may go through another mini cycle. You don't want to spike the nitrite/trates too bad at once. A small school of 6-8 is perfectly fine for a 20g.

Is it planted densely? Add in some floaters and plant heavily to eat up ammonia as they come. Many aquatic plants have an ammonia preference over nitrates.


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## Complexity (Jan 30, 2008)

Order your fish and put them in the tank. Feed very sparingly to help prevent a sudden ammonia overload. Then monitor the water twice a day. If you see any increase in ammonia or nitrite, you can dose Prime to protect the fish. If the ammonia or nitrite climb too high, you can do water changes to bring them back in line. At the very worst, you can always add Tetra's SafeStart which has the correct bacteria. Adding fast growing stem plants can also help as they will use any ammonia and nitrites in the water, helping to prevent them from spiking. Over the next few weeks, you can increase how much you feed the fish as your tank adjusts to the extra load.

To clarify, this is only necessary if you add a whole lot of new fish all at once. Otherwise, you should be fine.


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## Kworker (Oct 28, 2011)

I've once added 41 at once, had a loss of 2 (one black skirt terra and one oto) I only did it because at petsmart they were a buck each and I figured the die-off I had would be far less than if I left them all there which I honestly think so, loosing only 1 of each. I most would never do it again as I had to watch for a hawk for several days because if you add too much at once you can shock the beneficial bacteria and cause a recycle. Sorry of this makes no sense I tried, I'm a little too drunk right now


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## mitchfish9 (Apr 30, 2012)

Like I said this was hypothetical and I don't know what kind of fish or when it will happen. It's for the next time I wanted to order a schooling fish for a possible new tank. Assuming of course that it is heavily planted and it already has some other fish in the tank and has been running for at least a couple months.



Complexity said:


> Order your fish and put them in the tank. Feed very sparingly to help prevent a sudden ammonia overload. Then monitor the water twice a day. If you see any increase in ammonia or nitrite, you can dose Prime to protect the fish. If the ammonia or nitrite climb too high, you can do water changes to bring them back in line. At the very worst, you can always add Tetra's SafeStart which has the correct bacteria. Adding fast growing stem plants can also help as they will use any ammonia and nitrites in the water, helping to prevent them from spiking. Over the next few weeks, you can increase how much you feed the fish as your tank adjusts to the extra load.
> 
> To clarify, this is only necessary if you add a whole lot of new fish all at once. Otherwise, you should be fine.


Thanks, this is exactly the kind of answer I was looking for. I was kind of thinking the same thing.


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## flight50 (Apr 17, 2012)

Tank size has alot to do with it. A larger tank has more margin for error with its higher volume for dilution. I agree that you need to know your limit and not just throw any number in the tank. That's asking for a possible spike. Fish mass is the other part of concern. 12 neons will not equal 12 gourami's. Although shipping is expensive it will be more expensive if you have more losses than what its worth. This hobby is not cheap if you want successful tanks. Short cuts can bite you sometimes so be on your guard.

I purposely let my new tanks cycle for 5-6 month to let the plants get established. When I get to the point when I can add 2-3ppm of ammonia and its at 0ppm within 12-24 hours, then I know my toxin levels are of no concern.


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## OVT (Nov 29, 2011)

Increasing the water agitation (i.e. airstone, power head, etc) is not such a bad idea when adding a proportionally large number of fish.


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## Nubster (Aug 9, 2011)

Depends on how the tank was cycled and how long since it's been complete. If you used the ammonia (liquid) method and you add the fish right after the cycle is finished, you can add many fish because the bacteria is built up to handle a bio-load a lot more than the fish you are adding will produce. Once the fish are in the tank, the bacteria will reduce to match the load they are seeing. After that, if you add more fish, it needs to be done slowly.


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## Diana (Jan 14, 2010)

If the tank is less than adequately cycled for the bio load you need to add then use a product that contains _Nitrospira_. These are the actual species of nitrifying bacteria the tank needs. Read the label and do not waste your money on any other 'bacteria in a bottle' products. 

Adding liquid ammonia is a good way to see how well cycled your system is, and tests both the benefits plants and nitrifying bacteria. 

If the system can remove 3 ppm ammonia in 24 hours, and show only a minor blip of nitrite, and even this is gone in the same 24 hours then the tank is cycled well enough for a full load of fish at somewhat overstocked levels. (ie: setting up an African Cichlid tank)

If the system can handle only about 2 ppm ammonia I would not stock more than about half a load. 

If the system barely handles 1 ppm perhaps it would be safest to add no more than about 1/4 of a load. 

When you are ready to add more fish than about 10% more than it currently has, then get one of the _Nitrospira_ products to boost the bacteria population. These products can be kept in the fridge and used with each addition of fish.


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