Fish die after certain time

[Jayoneseven]

I have had a 29g tank for about a year and a half now.
I enjoy the tank, and subscribe to almost all methods of keeping it as good as possible for my fish. I do weekly water changes, 15%-25% depending, I vacuum the graven, clean the filter and change it periodically. I have maintained a very good water quality, and almost every time I check it the levels are just right. I have also kept ~10 living plants alive, which are flourishing and helping to maintain the water balance.
The problem is that I can not seem to keep my fish alive for more than a few months at a time. Generally they look healthy and social, eating and schooling, but after the 3-4 month mark they dwindle quickly, eventually being bullied then just giving up.
I have a mixed community tank, tetras, barbs, gourami, and catfish mostly.

The one part I don't understand is that I have an Opaline Gourami, he's almost a year old, and almost as big as my hand. He is always healthy, even while fish die around him. Surely if it were a tank issue he would have died also?
I buy all of my fish from Petsmart, could this be an issue?
I write this because my upside down catfish is currently lying almost comatose in some vegetation, yet three days ago he was just fine, I'm failing to see the connection as to why all of my fish seemingly become deathly sick and die, almost on schedule.
Any experience?

[fishmommie]

I have had a 29g tank for about a year and a half now.
I enjoy the tank, and subscribe to almost all methods of keeping it as good as possible for my fish. I do weekly water changes, 15%-25% depending, I vacuum the graven, clean the filter and change it periodically.


Water changes of 30 - 50% weekly would be highly recommended - that's what most here on the forum do. the lower % that you are changing could be part of the problem.

Also, when you say - 'clean the filter and change it periodically' - what does that mean? Do you replace your filter media? and if so, how often? If you are cleaning the filter media and or the filter in tap water or if you are replacing the filter media monthly or even every other month with new media, then this could be your main problem. Each time you clean in water that has not been dechlorinated, you are losing all of your beneficial bacteria colony. If you replace your old filter media regularly, then you are also loosing most of your beneficial bacteria. The end result is that your tank loses its cycle and most likely experiences an ammonia and or nitrite spike which would potentially poison and kill your fish. Never clean your filter or media in tap water. Always use old tank water or water that you've treated with dechlorinator. Also, never replace your filter media - even though instructions that came with the filter say to do so. Simply use it until it falls apart because that's where your beneficial bacteria is living.


I have maintained a very good water quality, and almost every time I check it the levels are just right.
When you say that 'almost every time I check it the levels are just right' makes me think that you are losing your cycle as stated above. A fully cycled tank will always read 0 ammonia, 0 nitrites and 5 - 20 nitrates.
I have also kept ~10 living plants alive, which are flourishing and helping to maintain the water balance.
The problem is that I can not seem to keep my fish alive for more than a few months at a time. Generally they look healthy and social, eating and schooling, but after the 3-4 month mark they dwindle quickly, eventually being bullied then just giving up.
I have a mixed community tank, tetras, barbs, gourami, and catfish mostly.

The one part I don't understand is that I have an Opaline Gourami, he's almost a year old, and almost as big as my hand. He is always healthy, even while fish die around him. Surely if it were a tank issue he would have died also?
I buy all of my fish from Petsmart, could this be an issue?
I write this because my upside down catfish is currently lying almost comatose in some vegetation, yet three days ago he was just fine, I'm failing to see the connection as to why all of my fish seemingly become deathly sick and die, almost on schedule.
Any experience?

Gourami's are pretty tough and can stand more harsh tank conditions than some fish - especially bottom dwellers. Toxins settle on the bottom and catfish and plecos are often victims of ammonia and or nitrite spikes.

So - having said all of this - could repeated loss of beneficial bacteria be your answer?

[ameliaaahx]

I have nothing else to add, excellent post from mommie.

[rodm81]

I think most people are gonna want to know how you are cleaning your filter. Since the BB lives there, you could be causing mini cycles depending on how you clean it. Most folks just rinse their filter media in old tank water and put them back in. Are you using a liquid test kit when you are checking your water parameters?

[VoidParadigm]

With the possibility of mini-cycles, that could be causing more sensitive fish to grow weak, and a weak fish is an easy target for an Three Spot Gourami to bully or steal food from, even if you don't see it happening.

[Jayoneseven]

Gourami's are pretty tough and can stand more harsh tank conditions than some fish - especially bottom dwellers. Toxins settle on the bottom and catfish and plecos are often victims of ammonia and or nitrite spikes.

So - having said all of this - could repeated loss of beneficial bacteria be your answer?

This definitely sounds like it could be the issue, the timing seems right too, I'm going to stop doing that.
I don't even know where I got into the habit of rinsing my filter, but now that I think of it, it's a terrible idea!

[Jayoneseven]

I had been rinsing it simply under tap water, which as I can now see is a big no no. Not sure why I was even doing that, and now that you've mentioned it, i see what a bad idea it was.
My main worry now though is I have my catfish who is looking like he's on death's door, and a smaller gourami who is floating by the surface a lot. I turned off my bubbles to try and remove some of the stress, and I plan on doing a water change tomorrow as soon as I'm able. Is there anything you can recommend I do to save the fish I've already harmed?

[VoidParadigm]

There's theories that bubblers help aerate the water, which could be a good thing for these fish.
Really, best thing is just make the habitat as suitable as possible for right now, and wait. Even if it means doing nothing.

[fishmommie]

Turn your bubbler back on. it will help with oxygenation in the tank

In the meantime you MUST do daily water changes of at least 50% to get the toxins out of the water while your tank is cycling again. Do you have an API liquid test kit? If not, you should invest in one asap. Test your water daily for Ammonia, Nitrites and nitrates. If ammonia and or nitrites approach .50 do an immediate water change. Your target during this cycle is .25 until both finally reach 0. If nitrates exceed 20, do an immediate water change.

Do not touch your filter media in the future. Just leave it.
While you may have to do daily or every other day water changes for a while to keep ammonia and nitrites below .50, eventually, your tank will complete it's cycle and you can begin a maintenance schedule of weekly water changes of 30 - 50%.

Once you achieve your cycle, do not add any new fish for at least a month. give the tank a chance to mature a bit. When you do finally add new fish, only add a very few at a time to give your beneficial bacterial a chance to grow to accommodate the higher bio load.
Keep asking questions if you have them and good luck

[Lady Hobbs]

I agree with posters above regarding the filter cleaning but another thought is the small water changes. I never change less than 50% a week and I run two filters plus stock very lightly.

I don't see anywhere you have mentioned your filter but most claim to filter "up to" a certain gallon but are really only good for just about one/half as they claim.

I don't know what kind of barbs you have but barbs are a good fish to stock as a species only tank. Especially if you have Tigers, Albino's or Rosie barbs. If you only try to keep a few of them then you'll have aggression issues, especially in a small tank like a 29 gallon.

You also mentioned you have an Opaline Gourami that's large. Another fish that's aggressive. I would save those aggressive fish for a larger tank and keep that 29 for a community of small fish.