(Semi-Urgent) Odd Zebra Danio Behavior + Space Issues

GoldfishAreBullies
  • #1
Before I begin, I'd like to start by saying that I really don't have much control over my situation outside of switching tanks for fish, and that while I know a good deal about biology, I lack much of the specific knowledge regarding fish.

I have one 1 quart (apparently these shouldn't even exist?) and one 10 gallon fish tank. Initially, I had 5 goldfish, 2 zebra danios, 1 tetra, and 2 fish I haven't identified. The two fish I haven't identified are generally healthy and are never really given any trouble by other fish nor do they give trouble, hence the lack of ID. They're similar in size to our zebra danios however.

For one month, these fish seemed to be living fine with each other in one 10 gallon tank (the previous occupant of which was one solitary goldfish that had been living there for years, so nitrogen shouldn't be a problem). However, one month in, the tetra disappeared with no corpse found, leaving us to believe it was eaten by one of the goldfish, the prime suspect being the largest one. A few weeks later, one of our zebra danios began acting strangely. It swam rapidly sideways, crashing into the floor repeatedly at high velocity: it was very painful to watch. The other zebra danio was fine, despite a week or more of co-living in the same tank since the behavior began, leading us to believe there was no disease involved.

Eventually, the crashing zebra danio became lethargic, and stuck to the floor for the most part, generally sideways. It began to be attacked by the goldfish occasionally, generally when they came close to it. They came close and seemed to nibble at it, followed by it quickly darting away, only to crash into the floor again. It only swam when food was coming, and even then, it mostly waited for the food to fall to the bottom, and as its condition worsened, it had to be nudged by its fellow zebra danio (which we nicknamed "the buddy"), when food was coming (on a side note, I never expected to see behavior this human from fish).

I had been suggesting that we move the zebra danio to another tank since it had been attacked, but it was only until some time later, when a large red circular injury appeared on its belly (cause unknown) that my family was finally convinced to move it. We put it in a one quart tank, where it remains today (has been there for ~1-2 weeks now. The injury has since healed, and it's a little less lethargic, though its swimming is still sideways, and it still crashes.

On trying to diagnose the danio's condition, I found a study, that isolated zebra danios to model human depression. On doing further research, I realized that if they were isolated, they might both become stressed, causing even more problems, so I suggested putting them both in the same tank. Though I quickly took this statement back considering the activity of the buddy, and the small size of the tank, the buddy was still moved, on the basis that it was being attacked by the goldfish, and was staying clear of them consistently, whereas it used to swim through or near them. Though both fish were very happy to see each other, I feel really uncomfortable seeing the once speedy buddy swimming into a corner, restricted by the walls of a one quart tank.

Can anyone diagnose the zebra danio? What should I do about the buddy? Is it better for him to stay in the main tank or the one quart tank? Are goldfish known for attacking other species? Though they're flashier, I would rather have the friendly and social zebra danios than the goldfish, especially after this incident, but my family is most likely unwilling to cull any fish.

tl;dr one zebra danio was behaving erratically and being attacked by goldfish so it was moved to a 1-quart tank (main quart size is 10 gallons). The other danio, despite being active and healthy was also moved in after being attacked by the goldfish. Read questions above

Though no fish is in urgent danger right now, I have read that small tanks can take years off a fishes life. Please respond asap if you know anything that could help.

I can't right now, but if necessary, I can also take photos, though videoing behavior quite like what it was at its worst is impossible, as one zebra danio is simply lethargic, lying down on its side, while the other is simply moving less, and often swimming into corners of the tank, most likely because of the safety and the small size of the tank respectively.
 
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Dray
  • #2
Unfortunately I do not have good news for you. Your tank is much too small to support your bio load. Your fish are almost certainly suffering from severe overcrowding and poor water quality. Even if they are still tiny, goldfish produce tons of biowaste for their size that your 10 gallon tank will not be able to process. Goldfish need around 20+ gallons per fish as a general rule.

Danios are shoaling fish and active swimmers. They need a minimum of 20 gallons so they have adequate swimming space and should be in groups of 6 or more.

If you can rehome all of the goldfish, the others will probably stand a chance. If not, you are going to see them sicken and die off one by one. The weakest fish will be the first to show the strain--in this case, it sounds like it's the danios. If a tank upgrade is possible, I would definitely do it.
 
PascalKrypt
  • #3
I think you should fill out the Fish Emergency Template.

From how you described the above story it seems - and I mean this in the nicest way possible - that you lack some important comprehension about the details of good fish care and I think we may be able to give you good, helpful advice if you give us the details of your care. This is just constructive commentary, don't take it personally. Lots of people that have fish don't know these things, some are just lucky enough to get away with it and others not so much. Most of the latter category.
 
GoldfishAreBullies
  • Thread Starter
  • #4
I think you should fill out the Fish Emergency Template.

From how you described the above story it seems - and I mean this in the nicest way possible - that you lack some important comprehension about the details of good fish care and I think we may be able to give you good, helpful advice if you give us the details of your care. This is just constructive commentary, don't take it personally. Lots of people that have fish don't know these things, some are just lucky enough to get away with it and others not so much. Most of the latter category.
Roger that, thank you for being so nice about it. In all honesty, I don't actually maintain the tank, it's maintained by my dad, I'm mostly an observer. I doubt he knows any more about husbandry and fish care (cycling) than I do, but I'll try my best to gather the info to fill this template.

Unfortunately I do not have good news for you. Your tank is much too small to support your bio load. Your fish are almost certainly suffering from severe overcrowding and poor water quality. Even if they are still tiny, goldfish produce tons of biowaste for their size that your 10 gallon tank will not be able to process. Goldfish need around 20+ gallons per fish as a general rule.

Danios are shoaling fish and active swimmers. They need a minimum of 20 gallons so they have adequate swimming space and should be in groups of 6 or more.

If you can rehome all of the goldfish, the others will probably stand a chance. If not, you are going to see them sicken and die off one by one. The weakest fish will be the first to show the strain--in this case, it sounds like it's the danios. If a tank upgrade is possible, I would definitely do it.
Thank you for confirming this, I had a vague suspicion since I first began looking into zebra danio care almost a month ago now that space was a huge issue. My family is probably going to think this advice as too generous and expensive (the tank isn't maintained by me) and not follow it, but it's good to have an idea of what to look out for the next time I visit the pet shop, and hopefully be able to save the fish.
 
ProudPapa
  • #5
I know you said your family doesn't want to rehome any of the fish, but as far as I know the only options are to do that or get a larger tank, and preferably several larger tanks.

As someone said, the danios are shoaling fish and do better in groups of at least 6, and more is better. The same is true for tetras.

Can you post pictures of the unidentified fish?
 

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