Suddenly Aggressive Fish?

lilfishy

Large Fish
Nov 27, 2002
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#1
We went away for a few days and had my mom feed the fish their regular food. Now, for some reason, some of the fish are dying and I have been noticing the angelfish and some of the other fish are getting aggressive (like really aggressive with fighting mostly with one another) and my pleco is also bothering the other fish. We have been home about a week and I have lost two fish so far. Why are my fish suddenly changing their personality? I did a water test and all seems ok except the Nitrates. I was told to put in some baking soda and salt and to get some live plants. The fish just don't look healthy though. Maybe they have Mad Fish disease? *laughingc
 

jclif1995

Large Fish
Jul 11, 2004
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#2
what was the nitrate reading? if it was high, you need to do a partial water change, along the line of 50 percent. aquarium salt is fine. i use it in both of my aquariums regardless of condition.

hopefully it is that and not the dreaded MFD.

keep us informed.
 

lilfishy

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Nov 27, 2002
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#6
Well...I have gotten the water all ready for the water change and will do that tomorrow or Saturday. As for the pl*co, I have been giving him extra algea treats the past couple days.

I put some more fish food in there just in case but my husband says I spoil them and not to feed them too much.

Hopefully they will straighten out. Should I get some live plants?
 

FroggyFox

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May 16, 2003
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#7
Do lots of research before getting any live plants...they can have a lot of special requirements.

Who suggested you add baking soda?? That could cause problems in itself...I wouldn't add any. Aquarium salt is suggested for some fish, and not for others...some people swear by it, but I haven't ever added any to my tanks except when I had mollies.

Do you have a test kit that measures in ppm or mg/l? Nitrates should be relatively low in the tank, and if they're high its a sign that you're not doing enough water changes (most suggest at least 30% every two weeks, most do more like 20-30% once a week) OR you've got too many fish for that size of tank (or not enough filtration for the amount of fish you have) or that you are overfeeding a LOT. Usually its reccomended that you feed once a day, about as much food as the fish will eat in about 5 minutes. You have to be sure to feed fish (like the pleco) what they need, and at the time that they'll eat it. Most plecos are more active at night...so the best time to feed them is right before you turn the lights out at night. If you mix up their food schedule it helps too. Get some bloodworms or hatch some bbs...cut up some cucumber for them or some lettuce for the pleco.

I dont know if it applies to fish...but temperature causes a lot of things to be more or less active/aggressive. Has your temperature been steady? What temp do you keep the tank at?

What size tank is this and what fish are in it?
 

lilfishy

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Nov 27, 2002
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#9
Lets see....I have a 29 gal tank with an emperor filter. I do water changes about every two weeks. I don't overfeed but we do have environmental water problems in this area. Toxic wastes in the ground and water.

I have a calico angel fish that is about 3 inches but he is not really big like the angel fish sometimes get. I have two golden angels that are younger and were really tiny but then got bigger so now they are about two inches a piece. I have two rummy nose tetras, a neon, three black tetras, rasbora tetra's(4). A Pl*co, an albino catfish and one female guppy. So in all I have 16 fish but some are small like the tetras. I feed the Pl*co algea disques a couple times a week and I feed the others once in the morning. Our water is extremely hard water. I add aquarium salt to the water and a ph stabilizer. The guy at the lfs who has been around like forever told me to use the baking soda. But he said to do it only for one day. He tested our water in the tank. It did seem to work for the nitrates for some reason but I don't know if its right or not and was willing to try it. He said the water was otherwise pretty good.

We once got some fish from a bad fish store that were sick with ick and the tank has not been the same since. We have had problems with fungal infections also.
 

lilfishy

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Nov 27, 2002
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#11
I started watching the tank closely and it looks like its the one golden angel that is doing all the harrassment of the other fish and getting them all riled up. He goes up to several fish and starts a fight. Do I keep a fish like that or do I get rid of it?
 

FroggyFox

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May 16, 2003
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#12
Totally up to you...You can try putting a divider in the tank or seperating that fish out somehow for awhile and see if a "time out" would help...sometimes it does. If not, then you have to decide which fish you like more. If you REALLY like the fish that is doing the picking...then you best find another tank or another home for your other fish, because eventually they will get stressed to death.

IMO a 29 is not big enough for 3 angelfish plus your other fish. Angelfish WILL grow to over 8 inches and if I had to choose I'd say to get rid of two of the angelfish and your tank would go back to being relatively happy.

As for the pH issue...I think that could be part of your problem. Listening to an employee at a fish store, no matter how much they sound like they know, is not always the best idea. Why dont you check out this article and do some reading around the board about why we dont generally suggest adjusting your pH.

http://www.myfishtank.net/forum/showthread.php?s=&threadid=18192
 

Lynn48

New Fish
Feb 4, 2018
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#13
So i have a question i have 4 black mollies and 6 zebra daminos in a 55 gallon tank oh and 4 fancy guppies my zebras started being aggressive towards my black mollies and they in returned started being agressive towards other fish oh and one catfish when i noticed the behavior i went to my local pet store and asked why a usually none agressive fish would start agression but had no answer for me
 

PURP

Small Fish
Nov 15, 2016
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#14
Hi. :)
I know this is an old thread, but I stumbled upon it by accident and thought someone else might too.

This probably sounds strange, but try rearranging the decor. In my 75g, every time I move things around, the social dynamics change quite noticeably within a matter of 24 hours. Especially with fish that have a propensity toward violence, their sense of calm comes from a carefully negotiated ‘peace talks’ of sorts, as to who controls which area of the tank. I have 6.5 yo red-tailed shark who becomes VERY irritable if his corner cave gets moved. Luckily my 6.5yo plec is 16” long and is kind of the sheriff of the tank... when she shoots across the tank, everybody else is IMMEDIATELY on their best behaviour. She’s not otherwise cranky... she even lets my Panda Garr nibble on her face (even her eyes!), and others often seek shade underneath her.

Sorry for drifting off topic, but I’ve witnessed the ‘changing decor’ thing for several years, and thought it might be a simple solution for someone.