Hopefully a simple question

[puber88]

I'm hoping this is a simple question with a mundane answer!

I have 10 zebra danios, and have just noticed that one of them has gotten very skinny, just wondering as to possible reasons.

But also, another danio seems to be swimming strangely, it seems to be swimming almost vertically upwards before sort of drifting downwards, it seems that the fish is having to constantly work to stay up in the water.

Has anyone seen anything like this? And is there Anything to worry about?

Thanks

JK

[fishmommie]

Hi Pubber.
Tell us about your tank to help figure things out. how many gallons, how many fish and what kind, what does your Ammonia, nitrites and nitrates read?
Is the tank cycled and if so for how long? What kind of filtration do you have and what's your maintenance schedule like (as in how often do you do water changes and how much do you change out?) this will give us an idea of what might be happening.

[puber88]

It's a 125l jewel with built in filtration etc.
has 10 zebras 10 black phantoms, 6 spotted Cory's a leopard frog pleco

Tank has been cycled for about 5 months, and fish only get added every 3-4 weeks!!

In terms of params, I don't do my own tests as I'm a beginner, my Lfs do them for me.

The tests always show good levels of all of them, but I can't give specifics!!

I carry out weekly 25% wc's, and have been carrying out more frequent ones recently due to a slight bacteria bloom (this cleared up in a week)

[fishmommie]

It's a 125l jewel with built in filtration etc.
has 10 zebras 10 black phantoms, 6 spotted Cory's a leopard frog pleco

Tank has been cycled for about 5 months, and fish only get added every 3-4 weeks!! In terms of params, I don't do my own tests as I'm a beginner, my Lfs do them for me. The tests always show good levels of all of them, but I can't give specifics!!

I carry out weekly 25% wc's, and have been carrying out more frequent ones recently due to a slight bacteria bloom (this cleared up in a week)

Hum. I would strongly suggest you get an API liquid test kit and start testing your water yourself. WE all test ourselves here because it's the only way to insure we know what our water perimeters actually are. I wasn't a beginner that long ago but have always tested myself.
The problem is, you can have ammonia spikes and not realize it. Depending on when you take the water to your LFS (before or after a water change) you could get readings that do not really reflect what's happening in your tank. Also, if you've recently had a bacterial bloom, it would suggest to me that perhaps your tank might not be fully cycled or you're experiencing a mini cycle.
It's critical to know what your ammonia, nitrites and nitrates read. Without knowing exactly what they are, if I were to hazard a guess, I'd say your danios might be suffering from ammonia or nitrate poisoning.
I'd start upping the water change to 50%. And I'd do one asap just in case you are dealing with an ammonia issue to try to get the level down.
Again - get that API liquid test kit. Generally the LFS uses test strips which are highly inaccurate so them telling you that your water is 'okay' really doesn't mean much.

Something else to remember - you're beneficial bacteria lives in your filters, not in your water so removing water cannot affect your cycle.

have you cleaned your filter since you set the tank up? And if so, how did you clean it? did you use tap water or old tank water?
is chlorine an issue where you live? if so, do you use a dechlorinator each time you do a water change?

[steeler1]

++ 1 to all of the above to fishmommie. For alot of years all I tested was the pH in my tanks and learned the hard way when an ammonia spike wiped out a whole tank last year. Know I test everything weekly.

[Brhino]

it does sound to me like both of your danios are dying. This may be due to issues that are beyond your control but it would behoove you to take the advice the folks here are giving to, so you can find out if the problem is something you could be preventing.

[puber88]

I always dechlorinate the water, and I only ever clean the filter in the tank water!!
I only squeeze the sponges once a month.

I will get onto the test kit ASAP!!!

I usually take the water sample pre wc.

Will do another wc tomorrow morning!!

Thanks

[steeler1]

Getting back to your original question, it sounds like the thin fish is wasting away, a condition i've noticed in Zebra fish the last few years.

I don't know if it's all the inbreeding but Zebra's used to be one of the most hardy fish IME. Before there was fishless cycling, I would use them over guppies to "seed" my tanks. I don't buy them anymore because the last few times they just wasted away.

Franks Aquarium had wild caught specimens a few years back that I thought about getting but went a different way.

[Cermet]

I always dechlorinate the water, and I only ever clean the filter in the tank water!!
I only squeeze the sponges once a month.

Thanks

Does not sound like you have a heavy load and as such, maybe cleaning the filter every month is a bit too much (the filtering ability does fall after even with a simple cleaning like that.) Maybe every other month would be fine.

[mermaidwannabe]

It would help us here in the U.S. to know what the equivalent of 125l is in gallons.

You say the tank has it's own built-in filter. Is that filter of great enough capacity to serve your needs? Usually, one needs a filter rated at least twice the volume or gallonage of the tank. You might consider adding an extra (external) filter, and seed it with established media so it grows the BB colony faster. I would recommend the Aquaclear hobs (I guess now they've renamed them Fluval). These are effective filters that are easy to maintain and access, and you can control their flow (somewhat) with built-in valves.

The danio that is wasting away may either be starving to death or it may have something genetically wrong with it. When you feed, do ALL of your fish eat? Are there any bullies that hog the food so that some don't get any?

You do need to do your own testing. The API master freshwater test kits have everything you need for testing ammonia, nitrite, nitrate and pH. It's important to follow the instructions carefully for each of the reagents.

The danio that is swimming erratically may have a swim bladder issue.

Do you notice any external symptoms such as rotting fins or lesions on their bodies?

Using a dechlorinator that neutralizes both chlorine AND chloramines is vital. This should be applied to new water BEFORE it enters the tank. I recommend Seachem's Prime. It has the added bonus of temporarily neutralizing a sudden ammonia spike, should you accidentally upset your existing cycle. It gives the filter a chance to catch up and re-establish it.

Finally, are any of your other fish bullying the danios? Is there one or more dominant danio that bullies the other danios? Stress could be breaking down the immune systems of your healthier fish, allowing disease and dysfunction to occur.

These are all things to consider...

Hope this helps.