Danio help!

[Nick121]

I just went to my LFS yesterday and picked up 4 more female zebra and leopard danios, previously the tank was more male dominated. I've had no issues with fin nipping, bullying and such but they're super active and crazy fun to watch.

After adding in the 4 to the group of 8 I already had, one of the smaller leopard danios began to isolate himself more to the other side of the tank. He looks perfect, swims fine, hangs out around the plants towards the bottom away from the group and comes up when I feed. My issue is that he seems to be a little slower than the rest? He will come up and look for food but won't eat, and then will retreat back away from the group. He's definitely smaller than most of the other danios but not unhealthy skinny.

They're all in a 75 gallon with plenty of spots to hide. Water parameters are perfect and the water is always around ~80 F°.

New to keeping danios, im aware they're known for being zippy and quick but this guy just seems to be a little slower and do his own thing.

I want to try and change what I am feeding to see if he reacts better but if there's any other recommendations let me know!

 

[Colin_T]

Pictures and video of the fish?
Upload video to YouTube, then copy & paste the link here.
If you use a mobile phone to film the fish, hold the phone horizontally (landscape mode) so the footage fills the entire screen and doesn't have black bars on either end.

Danios prefer cool water and if they are kept in warm water for too long, the females can become egg bound. It doesn't kill them but does make them fat and they can't breed.

Danios like temperatures between 60-75F (16-24C). But don't drop the temperature yet.
What other fishes are in the tank?

 

[TwoTankAmin]

I have noticed over the years that when I have fish in groups there is almost always a runt of the group. More often than not I believe this is a defense mechanism. The smallest fish cannot compete. So rather than risk being bullies it waits until it is safe to eat which often means it gets less food but also isn't getting beaten up by the bigger guys.

That said there is also another likely explanation. Sick fish tend to hide. They are doing so because they avoid being bullied by the others in the group. So, on should look for problems when they notice a fish behaving this way. Often an illness will keep a hungry fish from eating. This can be something as simple as being constipated to something more nasty like columnaris aka mouth fungus. It can also be internal parasites or worms.

When I was having bristlenose plecos breeding and had many offspring in grow tanks I saw how a few used the "don't fight the big guys for food" strategy to avoid being beaten up. When the biggest of the kids would reach shipping size and I began to sell them, I noticed that the little ones started to get more aggressive about feeding and they would start to catch up to the rest of the group size-wise.

 

[AdoraBelle Dearheart]

Do you happen to know whether the smallest one that's hanging back was from the new group? Or the new group? Although you'd likely see the same behaviour whether it's one from either group if it's behavioural, if one of the first group, then illness would be higher on my list for suspicion than it if's one from the old group that haven't shown signs of illness until now.

Anytime you introduce new fish, they need time to adjust to a new tank. Then, even the same species, the pecking order does need to be sorted out again. It's smart of the weaker/slower fish to let the most aggressive males battle it out first, and be cautious about getting into the thick of it yet.

Video of the entire tank and the weaker fish would definitely be helpful! Sometimes we can spot visible signs of illness, and the way the fish swims can reveal a lot about how it's feeling too, and what systems might be involved.

In the future though, it's always wise to quarantine new fish for a while (most do minimum two weeks to a month of QT) so you can observe the fish for any health problems, and because it's easier and cheaper to medicate a smaller QT tank if there is illness, than it is to medicate your whole tank! Or risk losing your whole display tank because new fish are high risk for introducing disease or parasites to your main tank.

But, the pecking order being re-established is very normal. You could try feeding a second food, or a food that floats in the water column for longer, that gives everyone a chance to get some. Something like cyclops or daphnia when defrosted into water and added to the tank are excellent for spreading out the food into a sort of cloud in the water column, and often used for fry, for that reason. Lets them all get a good chance of getting something to eat.

You could also try target feeding by feeding the main mob on one side of the tank, then target feeding the other, slower and weaker fish. With some fish, you can target feed with a pipette of some kind, but given how fast and zippy these danios are (I've kept them in the past, know what they're like!) I'd just feed a small amount on one side, sprinkle some in the middle and some at the other end. Give everyone a better chance, as they get settled in and establish a pecking order, and to make sure they're all getting some nutrition in the meantime.

Just be careful when doing this method as it's then very easy to overfeed the tank, and we're all prone to overfeeding anyway. So small amounts, but scattered, and clean up any that winds up sitting on the substrate without being cleaned up quick, since rotting food plus new additional fish increasing the bioload can cause an ammonia spike. Worth doing extra substrate cleanings and water changes when you add new fish, since it takes a while for the beneficial bacterial colonies to grow to manage the increased bioload.

 

[Nick121]

Hi! Thanks for all the helpful replies guys. I will link the video down below showing off the incident danio and the group he's in. To answer some of your questions, this is one of the danios I got with the first group of 8, before adding the 4 females. I can't say his behavior has changed much since adding the 4, but it's much more evident that he's slower and sticks behind, not necessarily skiddish or hiding. He kind of just finds a spot and sticks to it unless I feed to which he's at the top of the tank but not battling for food at all.

The tank is only stocked with the 12 danios so far, currently raising 5 fancy guppy fry to go in at a later date. I've got quite a bit of flow at the top of the tank that allows for the flakes to makes its way around the entire tank, which is unfortunate because he'll just watch most of the flakes go over his head. I just put some food in this morning and might have caught him eating a tiny bit but I could've been mistaken because a lot of them look similar and theyre so quick lol.

Heres the video.

 

[Colin_T]

It's a long fin danio, which is part of the reason it has trouble swimming with the other short finned ones. However, the fact it's isolating and not even trying to stay in the group is a bad sign.

Any chance of some clear pictures of the fish in question?

Drop the temperature to 75F and in a month's time, drop it to 70F.

 

[Nick121]

Best images I got for you on an iphone lmao. He's up with the pack now, still not as rambunctious as the rest.

 

[Colin_T]

Bit hard to tell but there doesn't appear to be anything wrong externally. Maybe he's just upset at having the long fins. Monitor and see how he goes over the next few months. Drop the water temperature too and see if that causes anything to change.