Filtration and Water Change Questions

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The nitrogen cycle is the natural processes that go on in your tank that convert ammonia into less harmful substances.

Ammonia gets into your tank through various pathways. Fish waste, decaying uneaten food, and dead, decaying plants are common ammonia sources in an aquarium. Its also possible your tap water is an ammonia source. Chloramine is a common water treatment and when treated with most water conditioners the bond in the chloramine breaks and releases ammonia into the water.

Ammonia can be toxic to fish, depending on how much there is, and what the pH and temperature of your tank water is.

The first stage of the nitrogen cycle is the removal of ammonia. If you have real plants in your tank some of this ammonia will be absorbed as part of their natural growth. Generally though ammonia is consumed by denitrifying bacteria that lives mostly on your filter media. These bacteria consume the ammonia and produce nitrite. Unfortunately nitrite is pretty much as toxic to fish as ammonia.

The second stage of the nitrogen cycle is the removal of nitrite. A different denitrifying bacteria will consume the nitrite and produce nitrate. Nitrate is much less harmful than ammonia and nitrite, and for most aquariums the nitrogen cycle ends there. Excess nitrate is removed through your regular water changes.

A further stage of the nitrogen cycle can also happen, but its difficult to remove all the nitrate from a typical freshwater aquarium. Plants will absorb some nitrate in a similar manner to how it absorbs ammonia to grow. There are also nitrifying bacteria that consumes nitrate and gives off nitrogen gas which will simply offgas from your aquarium. This nitrifying bacteria is difficult to grow in freshwater aquarium.

“Cycling” a tank is the process you go through to grow denitrifying bacteria in your aquarium to consume ammonia and nitrite. You are said to be “cycled” when you have enough bacteria to consume all the ammonia and nitrite that your tank produces and turns all of it into nitrate. If you test the water of a cycled tank you should see 0 ammonia and nitrite and some nitrate.
Wow, thank you for the explanation!

Now I have more of an understanding about beneficial bacteria and its importance. I'll start taking more tests and let you guys know to see how I should proceed.
A tank running 2 to 3 months should be cycled by now, and you arent reporting any issues so Im not too concerned, but knowledge is always useful.
So I ran tests on the big fish tank and everything looked good (low on all except Nitrates which is in the 5 ppm range). I guess I need to do water changes to lower the Nitrates? Or, should I get more live plants?

I've removed the powerheads and installed the big boy filter. So far, so good! But the neon tetras still stay in a corner on the bottom except during feeding. I was thinking of adding more neon tetras to get the others feel better.

Should I feed them twice a day? Or once a day?
5ppm for nitrate is really low. If you have live plants it could be too low.

One thing to do is make sure you are doing the tests correctly. If you are using test strips then i really wouldn't trust them. If i test my tanks with a test strip it tells me 5ppm nitrate, if i test using a liquid test kit it can be 20 to 40ppm. If you are using an API liquid test kit, really shake bottle #2 as instructed. Like bang it on the countertop. If you don't do this the test will give a falsely low reading. If you have a local fish store that does water testing maybe take a sample of water to them to double check your own test results.

Nitrate is the end product of the nitrogen cycle, and its much less toxic than ammonia or nitrite. For fish, lower is better. 5ppm is better than 10ppm, 10ppm is better than 20ppm etc. Typically 40ppm is where you dont want it go any higher, but if your regular weekly or fortnightly water change keeps it at lower levels that's much better for the fish.

Plants on the other hand need nitrogen. In aquariums they get this from ammonia and nitrate in the water. If nitrate is low then it could cause a nutrient deficiency. You mention getting more live plants, so i presume you already have some. If your plants show signs of nutrient deficiency and your regular water change is keeping nitrate below 10ppm then you may need to use a fertiliser with a good amount of nitrogen in it. Most aquarium fertiliser has practically zero nitrogen as its perceived to cause algae, which it doesnt. It might algae worse, but doesnt cause algae. If you are US based then NA Thrive is a good aquarium fertiliser that will increase nitrate, here in the UK we have TNC complete. Tropica and aquarium coop also do fertiliser with nitrogen/ nitrate in it.

Feed once a day, as much as is eaten in 2 to 3 minutes. If you want to feed more than once a day then dont feed as much as you would with 1 feeding.
Wow, really shaking bottle #2 made a big difference! It's hard to tell which orange it's at, but it looks like it's 10 ppm - 20 ppm. I haven't changed the water for about a week. I guess it's time? And I guess I don't need Thrive?

Do you think the tank is in a good shape so far? Would I be able to add around five more neon tetras? Do they need more hiding places (I removed a bunch of fake plants to make it more "open")?

Thank you so much!!
Im not sure if you have said what you already have in total. Will adding more neon tetras lead to an overstocking issue? Your photo doesnt look overcrowded.

Personally i like to do a big water change every week regardless of whether a water test says i need one. Some people are happy doing one every 2 weeks.

If a nitrate isnt elevating towards 40ppm with a weekly 50% water change you are probably good for a few more fish.

10 to 20ppm nitrate is a good range for a planted tank. If you arent dosing any fertiliser then the plants might still benefit from an all in one fertiliser though. You wont need one with nitrogen though.

As for hiding places, i would really look at getting a background to the tank as suggested previously, even if its just a piece of black card taped on the back of the tank. If you are planning on adding some more plants then a taller plant like an amazon sword at the back somewhere. Maybe a nice piece of driftwood will give you more height to your aquascape. The plants will all grow out somewhat and your java fern can easily be split into more plants to fill it out some more without you needing to buy more plants. You wouldnt believe how much java fern i have to remove and throw away to stop it taking over.
Thank you!

It doesn't look like it would be overcrowding since there's a lot of open space at the top area and minimal bottom decor/plants.

Do you have any recommendations for a non-nitrogen fertilizer? Or, is that Thrive too?

I have added a piece of driftwood, but it doesn't have many hiding spots on the piece. I'll try spreading the Java fern all over. How do you know when it's time for me to split the fern?
I use seachem flourish for an all in one liquid fertiliser.

You can just cut the rhyzome of java fern into 2 pieces and you then get 2 plants. They will grow. Or wait for little plantlets to appear on the leafs, they will grow into plants that can be picked off the leafs. With a little patience you could fill a tank with java fern all from just 1 plant.
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