Fish Dying

[cgweber]

Hello,

We have a 35 gallon tank. The last group died off slowly. Nothing out of the ordinary. We cleaned the tank, out in a new filter, and bought 12 new fish. All died in matter of days. It seemed like they were gasping for air at the top of the aquarium. Our home water test beforehand didn’t yield anything out of the ordinary. After the fish died, we replaced about 50% of the water. Test at Petsmart looked good ... twice. We got a smaller group of fish. Things didn’t look good again (fish at surface apparently gasping), so I added stress-zyme. It seemed to help, but not for 3 of the smaller fish. The three larger ones hanging on.

The water heat is about 78 and the sole plant I bought a week ago looks to be in tough shape. I also slacked on water changing when we were down to one fish prior to the 50% water change. From what I’ve read, my gut is we are low on oxygen, but It doesn’t show up in the water test and I don’t know why we’d be low.

Thoughts?

 

[Colin_T]

What sort of tank do you have, and how big is it (length x width x height)?
What sort of filter do you have?
How long has the aquarium been running for, and how long has the filter material been in the filter?
How often are you feeding the fish?
Are you dechlorinating the water before you add it to the aquarium?
What sort of dechlorinator do you use?
Do you have a fish only bucket that is used for the fish and not used for anything else?
What sort of gravel is in the tank?

What did the petshop test the water for (ammonia, nitrite, nitrate, pH) and what were the actual results (in numbers)?

Can you post a picture of the sick fish and a short video if possible?

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Do not buy anymore fish until this is resolved.

Stop feeding the fish for a few days.

If fish are ever gasping at the surface, or if any die, do a 75% water change (using dechlorinated water) and gravel clean the substrate each day for a week.

When we get more info we can try to work out what is going on

 

[cgweber]

Tank is 15x30x24. Using Aqueon Quietflow 30. Using Large Aqueon filter. Replaced filter after 50% water replacement about a week ago. We let it run for about 5 days before 2nd batch of fish. Using reverse osmosis water refills and always have. I use Aqueon water conditioner. I don't have exact readings, but the store did the Tetra 5 test strip and ammonia strip ... both times they said the water was fine or perfect. Fish that died are catfish, guppies, gourami, mollies, plecos. Sorry, I don't have any pics of the dead fish. We pulled them out fairly soon after they died and they didn't look much different than when alive. Am using Topfin premium white gravel. My plan is to keep doing 20% water changes unless/until the last catfish dies. Then do a 100% clean out. If it comes to that, should I get new gravel? Need the Aqueon 50 filter?

 

[fluttermoth]

It's extremely rare for a tank to have a dangerously low level of oxygen.

What's far more likely is that you have some ammonia or nitrite in the water; those toxins (especially nitrite) affect the fish's ability to properly take in oxygen through their gills, so it looks as if there is a lack of oxygen in the tank when that's not actually the case.

Of course, without numbers from any tests, I can't be 100% sure, but as you put in a new filter, you will have lost your beneficial bacteria, and just letting a tank run won't allow any to grow, as they need ammonia as food.

Are you adding any remineralising salts or buffers to the RO water? RO water cannot be used for fish as it is; all fish and plants need some minerals in the water and they will not live long or be healthy in pure RO; especially fish that need hard, alkaline water, like guppies and mollies.

I would advise you to get some test kits of your own and look at doing a proper fishless cycle before you think about restocking. It would be a good idea to find out the details of your tap water re hardness and pH (you can find that information somewhere on your supplier's website) and choose fish that will do well in it, rather than trying to change it.

 

[seangee]

If I read this correctly you changed your filter. That means your tank has an "uncycled" filter and you should be treating it as a new tank. click on "How to tips" and read the "Cycling a tank" section.

 

[**sarahp**]

out in a new filter, and bought 12 new fish. All died in matter of days.

Agree with Sean - I read that as you put in a completely new filter - if so then you are doing a "fish-in" cycle and your fish are suffering from ammonia poisoning.You need to do 75% water changes everyday until the tank is cycled - which could be several weeks.

 

[cgweber]

I did take the water in a few days after I changed the filter and there was no ammonia reading. I have since done a lot more reading on the nitrogen cycle and am hoping my problems have to do with removing the filters and removing any bacteria. I would don't think I would call myself even an intermediate fish owner, so I am still learning.

I have read my Aqueon 30, while adequate, may not be enough especially w/ plants. I read several people use 2 Aqueon 30's instead of a 50. So, I added a 2nd Aqueon 30 filter and I'm going to let the water cycle and do frequent water changes before we get more fish. I didn't get a good answer on how often I'm supposed to change the filter. Since I have 2 filters now, I suppose I can stagger the changes now? How often should I change the filters.

Also, regarding the reverse osmosis water. Our water is extremely hard, so we have a water softener. If I used the untreated water, it would cover the tank with hard water deposits in a matter of weeks. I chose RO water as the alternative to water treated w/ the water softener. Would the softened water be better than the RO water? If I stuck with the RO water, any suggestions for a mineral additive?

One catfish is apparently still alive, so that's good news.

Chris

 

[Colin_T]

Use a Rift Lake water conditioner at 1/3 to 1/2 strength to increase the hardness of your reverse osmosis water. Or use half R/O and half normal water.
If you use mains water then use a dechlorinator to remove chlorine/ chloramine, and aerate the water for 30minutes or so before using it. Same deal with R/O water or well water. Aerate it for 30minutes or more before using it to get the dissolved gas levels correct.

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Don't get another Aqueon hob filter. Get an Aquaclear HOB filter. They can hold 3 sponges (or sponges and carbon if you want to use carbon) and are much easier to work with.

When you clean the filter, wash or squeeze the filter materials in a bucket of aquarium water and then put them back in the filter. If you have a carbon cartridge, then throw it away and replace it with a sponge or white filter mat.

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If you can post a picture of any sick fish we can see if there is a disease affecting them.

 

[seangee]

I have read my Aqueon 30, while adequate, may not be enough especially w/ plants.

Plants, especially fast growing ones, remove ammonia from the water so a second filter may not be neccessary as the plants actually assist the filter.

If I stuck with the RO water, any suggestions for a mineral additive?

Do you have access to a tap (say an outdoor tap) that does not go through the water treatment system. Mixing tap water with RO water is an effective way of reducing hardness without getting rid of all the minerals.