Corydora tank stocking?

[Jasmine_aquatics]

Hello, I have a 75 litre (20 gallon) aquarium with only 3 livebearers in it currently. The tank has been running for over 2 years but I have had it under stocked for the past 6 month's. I am getting some corydoras this afternoon and I know they like being in large groups, so my question is can I get 6 at once today (so I will have 9 fish in total in my aquarium) or will this overwhelm my filter? Bear in mind my tank is mature, but has been understocked for a while... Any answers appreciated

 

[itiwhetu]

This is a great question. Personally, I wouldn't load your tank. As a rule of thumb, I would never more than double the load of a tank. So, my recommendation is adding three Corydoras. Which is double the load, then in a month you can add six Corydoras, which is doubling the load. Just be patient, take your time.

 

[DoubleDutch]

You can to me, but feed a little the first time and keep an eye the levels.

What species ? Single and plural is Corydoras btw

 

[itiwhetu]

You can to me, but feed a little the first time and keep an eye the levels.

What species ? Single and plural is Corydoras btw

 

[DoubleDutch]

The OP wants to add 6 Corys in the end not 9 (9 fish)

 

[CaptainBarnicles]

The OP wants to add 6 Corys in the end not 9 (9 fish)

So add 2 then 4 next time

 

[itiwhetu]

The OP wants to add 6 Corys in the end not 9 (9 fish)

Whoops

 

[itiwhetu]

So add 2 then 4 next time

Or three and three, you get the picture. I hope!

 

[Jasmine_aquatics]

Hello, I have a 75 litre (20 gallon) aquarium with only 3 livebearers in it currently. The tank has been running for over 2 years but I have had it under stocked for the past 6 month's. I am getting some corydoras this afternoon and I know they like being in large groups, so my question is can I get 6 at once today (so I will have 9 fish in total in my aquarium) or will this overwhelm my filter? Bear in mind my tank is mature, but has been understocked for a while... Any answers appreciated

Thanks everyone for the replys, I think I will just add 4 for now and 2 more in a month's time but I will check the water for the next few days and feed only a tiny bit

 

[Sgooosh]

So add 2 then 4 next time

then add 8 then 16 then 32 then 64 then 128 then 256 then 512...
that is what i want to do, whenever i see a bronze or emerald cory I NEED

 

[CaptainBarnicles]

then add 8 then 16 then 32 then 64 then 128 then 256 then 512...
that is what i want to do, whenever i see a bronze or emerald cory I NEED

Good maths!

 

[Byron]

When acquiring a shoaling species like Corydoras, it is always better to add the entire intended number of the species at the same time whenever this is at all possible. The fish will without question settle in faster the more there are, and this means much less chance of ich or similar issues. Other reasons which do not apply to all shoaling species can involve the establishment of an hierarchy, or certain other species may be territorial. But regardless of the specifics, this is always in the best interests of the fish themselves.

The tank size and setup then comes into play. This is where plants, and especially fast-growing plants like floating species, will really benefit. It is virtually impossible to add too many new fish to an established aquarium containing such plants, always assuming the intended number is within the range of being safe to begin with. As an example, if my 40g tank has a surface cover of floating plants like Water Sprite that are growing so fast they need to be thinned out at every weekly water change, I can add 20 or 30 or even 40 Corydoras at the same time if the tank is not already anywhere near its maximum bioload.

Without any plants, relying solely on the bacteria...something of a different story. I would not push the envelope.

 

[Colin_T]

Since the tank is 2 years old, I would add all 6 at the same time. This reduces the chance of introducing new diseases into the tank. There is still a risk but you are only adding new fish once, not twice.

Your filter should be fine. If you are concerned, monitor the water quality for the next week and do a big water change if you get any ammonia or nitrite readings.