What is a safe number of fish to add at a time?

[Snagrio]

My 125 gallon will soon be ready for new fish (going to wait a couple weeks for plants to grow in) but my question is what's the generally recommended numbers you can add at a time for a tank that size? The species I'm planning on are all small schooling ones (tetras, cories, hatchets, ect.) and maybe some dwarf cockatoo cichlids (still unsure on the final "centerpiece" slot).

The tank itself has an established bacterial colony and just recently had a few fish readded after renovation work has been done (two bristlenose, a giant danio and Australian rainbowfish, the latter two living out their twilight years as the last of a previous tank) so it's not a new system.

In the end I'd like a dozen of each tetra (going with a mixed shoal of neons and black neons), a dozen hatchets (if I can't find marbles silvers will suffice) and at least half a dozen corydoras (probably pandas but I'm not sure). Would it be safe to add 12 fish at a time or would half that amount of better?

 

[jonny-5]

If it was me i would add a school of 6 at a time, 2 weeks later add another school. You may get away with adding more but just to be safe.......Safety in Low Numbers ?

 

[itiwhetu]

I agree just 6 -10 at a time. I always just add one species at a time as well. Why I do that I'm not sure, it is just what I do.

 

[Snagrio]

Sounds about right as to what I was thinking then. Also due to how long renovations took to the point where there was a period when the filters (two Cascade 1500 canisters) were shut off for 48+ hours, and then spent a couple weeks running essentially just empty water, I'll want to wait a while and add slowly by default to give the rebuilding bacterial colonies time to catch up.

Will certainly keep a close eye on water parameters for the time being as well now that there's new waste actively going through the system again.

 

[itiwhetu]

As long as you have plenty of live plant it will get going pretty fast. Once you see growth on the plants you are good to go.

 

[Retired Viking]

When I first silent cycled my 55 gallon tank I add a shoal of 5-6 tetras and then waited a week tested the water and added another shoal until I had around 35 fish mostly tetras. You can go faster but this way I could add more plants if needed and it was safer for the fish. I was getting back into fish keeping after a long absence and this was the first time trying silent/planted cycling. Since then I had set up 2 more tanks and added fish a little faster depending on size of the fish and how many plants in the tank.

 

[Colin_T]

If the tank has been cycled, you can add all the fish at the same time. That is the purpose of cycling an aquarium, to build up the beneficial filter bacteria so you can add fish.

If you are getting neon tetras, buy them all at the same time. Don't buy 6 here and 6 there because there is more chance of disease. By 10-20 or however many you plan on getting and get them all at once.

Hatchetfish should go in last and make sure everything is good before you add them.

Any fish that gets added to the tank should be quarantined for at least 2 (preferably 4) weeks before it is added to the main display tank. The exception to this is when you add the first lot of fish to the main display tank. There is no need to quarantine them because there won't be any other fishes in the display for them to infect (assuming they have a disease).

 

[Naughts]

I agree with Colin, add the whole shoal. If you split it you double the chance of disease and double the aggrevation of the fish sorting out their pecking order. Also, more is always better for relaxed shoaling fish so why cut it back to the bare minimum of six at the most stressful time? They are already traumatised from being netted and moved, probably several times over.

And with little fish in a 125 gallon there is nothing to worry about.

 

[Snagrio]

As long as you have plenty of live plant it will get going pretty fast. Once you see growth on the plants you are good to go.

More are actually coming in within the next couple days (none of the stores around here seem to carry over half the species I was looking for so I went to online) so there will be much greenery to be sure.

If the tank has been cycled, you can add all the fish at the same time. That is the purpose of cycling an aquarium, to build up the beneficial filter bacteria so you can add fish.

If you are getting neon tetras, buy them all at the same time. Don't buy 6 here and 6 there because there is more chance of disease. By 10-20 or however many you plan on getting and get them all at once.

Hatchetfish should go in last and make sure everything is good before you add them.

Any fish that gets added to the tank should be quarantined for at least 2 (preferably 4) weeks before it is added to the main display tank. The exception to this is when you add the first lot of fish to the main display tank. There is no need to quarantine them because there won't be any other fishes in the display for them to infect (assuming they have a disease).

I agree with Colin, add the whole shoal. If you split it you double the chance of disease and double the aggrevation of the fish sorting out their pecking order. Also, more is always better for relaxed shoaling fish so why cut it back to the bare minimum of six at the most stressful time? They are already traumatised from being netted and moved, probably several times over.

And with little fish in a 125 gallon there is nothing to worry about.

I guess that would work. Have been considering ordering online since, even with the shipping, buying such fish "in bulk" would be more cost-effective which is why I was asking about essentially doing it all in one or two batches instead of several trips at a time.

However, I'm not sure if I'd be able to quarantine. For one thing all I'll have to work with is a 10 gallon that's currently empty. The old 55 I'm going to put up for sale soon and while I have a 30 gallon, it's currently already inhabited by my ball python (he'll move out of it but it won't be until much later in the year as he's still a baby). And secondly my mother wouldn't be pleased to hear about it as she's been staunch on only one tank running due to electricity costs I guess, even if it's temporary. Really this whole project has been getting on her nerves due to delays and constant back and forth issues so I'm trying to be in her good graces as much as possible.