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I have a 55 gallon tank.
I bought it used cleaned it and cycled it.
the water tested fine so I bought a few mollies.
the ammonia level skyrocketed immediately. I did a water change and new treatment but the mollies died.
I managed to get nitrate/nitrite normal and ammonia to a very low level and got more fish. My ammonia went up again, but this time only the mollies had problems.
I have two inch-long angels that are fine and a rubberlip pleco that seems okay when he comes out. But my mollies won't stay alive and I am having ammonia level issues.
Any advice?

If the ammonia level is measurable, your tank has not cycled.

How did you "cycle" it originally? What did you use to seed the tank with bacteria (something from an established tank? A commercially-available liquid?)? What did you use to provide a source of ammonia before you added the fish?

Before you add any more fish, make sure the ammonia goes away. This could take a month or longer. Now that you have fish it's not safe to do the "fast" method of fishless cycling by adding ammonia to the tank directly. When you do add fish, do so slowly. It's tempting at the store to pick up a lot of fish, but the more you add, the more the ammonia will spike in response as your filtration catches up with the new load.

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When I started I filled the tank and treated it with aqua safe and easy balance then ran it for a week. That's what I was told to do by the person I got it from.
I've only ever added 3-4 fish at a time and all under 2 inches long. How can 4 2-inch mollies overload a 55-gallon system if I'm supposed to be able to keep more than 6 times that amount in the tank?

After we put the first set in, two went back because they had fungus show up within a day. We had already used the ATM Colony at that point and were told to try a fungal treatment just in case. After that, we've only ever used Aqua safe, easy balance, the ATM Colony and Paradigm, and ammonia clear on the tank. These products worked fine with my 29-gallon, which has been up for a year and tests clean.

One other prpblem I'm having is that water changes don't seem to be helping. All I read about is doing a water change will solve all your problems. Every time I do a water change and test the water again for ammonia, there isn't a difference. Given how sensitive angels are said to be, I don't want to do 50% changes every day, but that seems like the only way to fix this.

BTW- tank currently houses 1 2-inch molly, 2 smaller angels amd a 2.5 inch pleco. It has never had more than 7 fish at a time all under two inches long.

Hi and welcome to Fish Profiles!

Used tanks can house problems, how did you clean it? A weak, diluted, solution of regular clorox and water is one of the best ways. Then a through rinsing and refil the tank and add a lavish amount of declorinator. When you cannot smell chlorine in the empty, dry tank, then you can refil it and start using it.

Mollies are not a great fish to cycle a tank, and, they have vastly different needs than the angle fish and plecos.

You are right with your comment about two small fish causing toxic ammonia levels so rapidly in a 40G tank. The gravel would have to be filthy with waste products and someone else besides you would have to be feeding the fish without you knowing it.

The test kits that we use to measure the ammonia, measure all forms of ammonia. When you add chemicals to "remove" or "neutralize" any ammonia present in the tank, it changes for chemical form of the ammonia to one that is non-toxic to the fish...But... it is still ammonia and will register as such. Generally speaking, a small amount of ammonia, say 0.25 (or a trace) is a normal. The "key" is to monitor the Nitrite and Nitrate levels as well. Measure daily and keep a record for the first 4-6 weeks. Over time you will see the NitrIte level climb, and then drop off as the NitrAte level begins to first register, and then climb. As those two values rise and fall, the ammonia level will drop.

If you use fish to cycle the tank, then realize that the levels of ammonia and nitrIte will rise to near toxic levels and affect the health of the fish. If you choose to remove/replace the water during that time to ease the suffering of the fish, you are "diluting the soup" the aquarium water, and that will lengthen the cycling process. Fishless cycling is the best.

Unless you use one of the products that "instantly" cycles the tank, you should know that it will take 4-6 weeks for that tank to cycle.

If your angels and the plecos are swimming normally and eating when fed, I would continue to test and forget the mollies.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

I used a diluted bleach solution and scrubbed all the residue out before rinsing and filling the tank. the gravel and plants are all new.

What do you mean "mollies aren't good to cycle a tank"?
I wasn't trying to cycle with fish in the tank. I was trying to do the fishless cycle.
My 29 gallon didn't do this and I didn't do anything different with this one.

Can I just not have mollies? Cause the list of fish that go with angels isn't long as it is. My other angel lives with several unusual species, but not having the ammonia problem I added him last, not first.

Hi,
Mollies are not good companions for Angel fish or for the Plecos. Mollies prefer harder water, up to as much as a pH of 8, and should have some salt in the water. Angel fish and the others prefer much softer water, with no salt. Take a minute go read the information on these fish and see what these fish require.

If you are doing the fishless cycling method, then you should be adding pure, unscented ammonia, to the tank. As it is "fishless" there should be no fish in the tank dring this process until it is fully cycled.

I guess I'm not seeing all of the notes that you have posted when refering to this tank and its problem. It will take 4-6 weeks to cycle the tank and You will need to perform at least daily, and preferably 2x/day testing.

As you know you will see the ammonia level rise, followed later by the nitrite level. You will need to hold the ammonia level constant through the first stage of the cycle. Once the nitrates start to occur, the ammonia level will begin drop until it finally disappears (goes to zero). As the nitrite level starts to drop and nitrate level starts to rise it will take more ammonia to maintaintain the required initial reading. When the ammonia level and nitrite levels drop to zero then your tank is cycled and you cease adding ammonia, and you can add the fish. Depending upon your initial starting level of ammonia, you tank will readjust to the new fish and their amount of waste products, so you should expect to see some changes. If the fish give off more ammonia then the tank will "mini cycle" as the nitrate colonies build in size to handle the higher amount of ammonia. Depending on how much more ammonia the fish put out that "mini cycle" should only take a week or two to reach the point where the nitrite disappears and the nitrates increase.

That's the "normal" way to Fish less" cycle a tank.

There are now, on the market, products that contain active bacteria. Be sure that if you use this type of product that it is not out of date, and if it needs to be refigerated, that has been. Read the label. One dose, or sometimes one bottle full is good for "X" number of gallons. This is live bacteria and will nearly instantly provide the needed nitrate colonies. To maintain those colonies, you need to add fish within a few hours to a day. If you do not provide the ammonia necessary to feed the colonies (add fish) then the colonies will die off, and if you have waited too long, the tank will instead begin the Nitrogen Cycle with the ammonia from the fish that you have put in the tank.

Hope that this helped...
Frank

-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--