Hi everybody.. i'm brand new to this hobby, as we just got a hand-me-down tank from the family and decided to use it. I got really intrigued and jumped in but I think I made a few mistakes.

We have a 12 gallon (roughly from my calculations) hexagonal tank. Initially we set the water up with filter and heater for about 4 days and then added 2 snails.

About 3 days later we got a handful of fish, which I think was a bad idea because we introduced them at the same time.
We bought 3 danios, a guppy, a tetra, and 2 ghost shrimp.

about a week later we added another guppy and a tetra.

I was using the rule of thumb for 1 gallon per inch of fish, but ignoring the snails because they are usually at the bottom or on the walls... however, I think we over-crowded the tank. That, and I definitely learned that we shouldn't have introduced them all at once.

One tetra died pretty quickly, it wasn't eating and just hid the whole time. Then my original guppy died the other day. I noticed he wasn't as colorful and started getting really pale and light along his back and stomach - but when I took him to the pet store they said he was fine.

They said my ammonia levels were too high, so I bought one of the $3 ammonia remover filters (I was advised to just toss the filter in the tank directly - not in the filter itself - for a week).
Aside from the ammonia they said my water was fine.


I'm trying to learn and graduate to a bigger tank once I know what I'm doing - so does anyone have any ideas why those two fish died? Anything I may be doing wrong (outside of overcrowding)? Anything I should look for or test?


Thanks in advance, and sorry for the novel.

Being a beginner fish keeper means feeling bad about killing some fish, doing a little bit of reading, and changing what you're doing so it won't happen next time. We all go through it. I killed probably a dozen fish when I was first starting out. But that's why you learn, so you won't do it again next time. Don't feel too bad.

Establishing the nitrogen cycle (getting ammonia converted to nitrite converted to nitrate) takes 40 days. Check out slide 8 of this powerpoint for a graph: http://www.ag.auburn.edu/~davisda/class ... Design.pdf

That's why most people do fishless cycling. Here's an article about it. Article: http://www.fishkeeping.co.uk/articles_5 ... rticle.htm You basically just add fish flakes every day as if you were feeding fish, but without any in the tank. The cycle happens just as if there were fish in the tank, but without any having to suffer. After 40 days you can add fish and they'll never be exposed to ammonia or nitrite. Then you do water changes once a week or so to keep nitrate below 40 ppm.

And here's some information about why growing plants would have helped prevent your fish from dying. http://theaquariumwiki.com/Plants_and_B ... Filtration

+1 to what Natalie265 said.

"When I spoke to someone at the fish store they said I could just transfer the existing water over and let the nitrogen cycle complete in the new tank with the new water."
The nitrogen converting bacteria live on surfaces, not in the water column. The sponge-like material in your filter is important. The water in your old tank is not. Put the old filter on the new tank, making sure to keep it wet and not let it dry out during transfer.

Drip acclimation works like so: http://www.youtube.com/watch?v=ZSnJjTEjWyU

About overcrowding:
When you add food to your fish tank, the nitrogen in the proteins in that food are broken down into smaller molecules like ammonia. This ammonia generation is entirely dependent upon how much food you add, not whether or not your fish eat it. Flakes sitting uneaten on the substrate contribute to the ammonia in the water, too.

Now, once ammonia is present in the water, you have to get it out fast. If it builds up to even 2 ppm it can kill your fish. It is very, very toxic. You can do one of two things to ammonia: Convert it to something less toxic or remove it itself. The first, the conversion, is done by bacteria, whose end product is nitrate which is not toxic until 40 ppm or so. Toxicity depends on the fish species, but in general we're talking about the same nitrogen atom that was extremely toxic at even 1 or 2 ppm as ammonia being much much less toxic as nitrate. You are then able to remove the nitrate weekly with a water change, diluting the concentration and keeping it at a safe low level. The second method, removal, is done when plants eat ammonium, which ammonia is in equilibrium with. By pulling ammonium out of the water, the nature of equilibrium means that the amount of ammonia decreases as some ammonia becomes ammonium to compensate for the drop in ammonium. Then the growing plants eat more ammonium, repeat repeat repeat, and the ammonia is in the span of a few hours reduced to 0 ppm.

Now, overcrowding (it's taking me a while, but I will get to the point!). Overcrowding is when the amount of food added to the tank overwhelms your removal method and the net concentration in the water becomes greater than 0 ppm. If the tank is not overcrowded, the plants/bacteria are able to remove the ammonia at the same speed that it is generated, so the total amount present never gets above 0 ppm. But if you have too many proteins breaking down at one time, you can get ammonia in the water.

You'll have to excuse me but as a chemical engineer there is one thing hammered into my brain that I can never forget, and that is a mass balance:
Accumulation= In - Out + Generation - Consumption
In the world of fishkeeping, this translates to:
Ammonia concentration in the water = Fish food added - Mulm siphoned out + Fish dying and rotting - Plants eating ammonium

So. What are some ways to avoid overcrowding? There are two methods.

One, you can increase the volume of the tank. The way concentration works is that if you have X number of ammonia molecules, let's say 1. Now if your tank is 1 gallon, that's 1 molecule per 1 gallon, 1/1. Increasing the volume of the tank would dilute the concentration. If you have a 10 gallon tank that same 1 particle becomes 1 molecule per 10 gallons, 1/10. With a 55 gallon tank you're taking that 1 particle and diluting it in 55 gallons, 1/55. See?

The second method is to increase your conversion or removal method. For example if the bacteria/plants can eat 5 ammonia particles per hour and you add 5 per hour, the net ammonia concentration in the water is 0 ppm. Now if you add more food (because you added more fish) and all of a sudden you're adding 7 ammonia particles per hour and your bacteria/plants can still only handle 5 per hour, then the ammonia will start to accumulate and the concentration will become nonzero. You would have to either increase the number of beneficial bacteria or the number of plants. One example of a way people increase the number of beneficial bacteria is by using a filter with a larger surface area. This website, http://www.bioconlabs.com/abtqs.html claims that waterfall hang on back filters have 200 square feet of surface area per cubic foot of filter media, and that fluidized bed filters have over 6,000 square feet of surface area per cubic foot of filter media. You can think of square feet of surface area as being analogous to houses. The more houses you have, the more bacteria-people can move in. So by switching to a fluidized bed filter, your population of beneficial bacteria can be much larger. Or you can add lots of plants. Diana Walstad wrote a very interesting book called "Ecology of the Planted Aquarium" that was all about using plants and plants alone to filter aquariums. Her tanks are wildly popular, and for good reason. The plants eat all the nitrogen waste, so you don't have to water changes nearly as frequently. For example, my own tank is very heavily planted and no matter how long I go in between water changes the nitrate never rises above 10 ppm. But that's a different story. If you want to know how to keep plants alive, just ask me, and I'll talk way too much about that, too, as I have so far with this post ::blush::

But anyway, my point is, overcrowding is really all about how much ammonia conversion/consumption is going on in your tank. And about how many volumes you have to dilute the ammonia. A larger tank is better. Using the filter from your old tank is a good idea. And no, you don't have to transfer the existing water.

Here is the latest video from my own 55 gallon tank. I use a kitty litter substrate ( http://www.thekrib.com/Plants/Fertilize ... jamie.html ) and $30 full spectrum shop lights from Home Depot (lights are cheaper when not marketed to pet owners). Video: http://www.youtube.com/watch?v=LnVXXwbIU5U
Ammonia and nitrite are constantly at 0 ppm and the nitrate never rises above 10 ppm no matter how long I go in between water changes. Check out "Ecology of the Planted Aquarium" by Diana Walstad. Plants are cool.

I'm glad I can help :)
Thank you for actually reading what I wrote. A lot of times I write stuff that long and wonder if people just ignore it because it's a text wall. So thank you, I appreciate you reading it :)

You can put your existing fish in the larger volume if you want. That would dilute their waste and make it more likely for them to survive this ammonia period. The peak ammonia concentration is going to be higher and more deadly in the smaller tank than it is going to be in the larger tank given the same waste load, because a larger volume dilutes concentration more. If you feed both tanks with fish food every day as if there were fish in them, they will both cycle. The fish can be in either tank; their presence doesn't matter to the cycle. So they might as well be in the larger tank, where the maximum ammonia concentration won't be as high.

Any nonzero ammonia value means that the bacteria will be increasing in population because there's more food for them. But if there's an ammonia concentration of 5 ppm or of 0.5, that doesn't increase their replication rate. Bacteria can only divide so quickly. So you might as well put the fish in the tank with the 0.5 ppm concentration.