Oxygen in tank

[Confusedpanda22]

Hi all

I'm currently cycling my tank and only have 2 plants in it at the moment but will put more in soon.

I've been reading all sorts of stuff about plants and oxygen, lots saying you need c02 and others saying you don't. Will adding in air stones help at all? c02 just seems quite intimidating for a beginner.

Maybe I'm just jumping the gun but I don't want to get everything in and then find out later it's all going wrong due to a lack of oxygen.

I'm just at that beginner tank stage where I'm reading about everything and this forum has proved more useful than anywhere I've found online yet.

Oh yeah it's a 300l tank with a with a fluval FX 4 filter.

Thanks
Tom

[Netsu]

All of the plants in my tank are Tropica brand, and are classed as “easy” (beginner plant). I don’t have a CO2 set up (and don’t intend on ever getting one) and the majority of plants have flourished. I use root tabs (as I only have sand as my substrate) and also a liquid fertiliser.

As for oxygen I have heard differing things too. I ensure that my filter outlet points upwards to agitate the surface. I also have airstones (which I have on timer) but I think this is more for aesthetic purposes!

My most successful plants have been Amazon sword, Java fern, moss and anubius (attached to wood and rocks), cryptocoryne and hydrophilic polysperma to name a few! I’ve had no success with floating plants.

[LookoutTrout]

Hi, oxygen comes mainly from surface agitation which an FX4 can provide more than enough of. The only time you might want to reduce agitation is if you are adding CO2, which despite what some websites say is not necessary at all. You might want CO2 if you want a perfect plant setup but if I'd recommend starting without and then adding it after the tank is stable if you aren't happy with your plants. You can easily have a lush green planted tank without it.
You won't need an air stone but can add one if you like the effect.

[Lo1]

This is from fish lab:

Why is surface agitation so important?

The most compelling argument for surface agitation is self-explanatory…

It oxygenates your water!

As you are no doubt aware, the oxygen that your fish breath works its way down into your tank from the surface…

The bigger the surface area of the tank, the more oxygen can penetrate the water.

Now, ordinarily the water surface area is determined by the size of your aquarium.

A 4 ft x 2 ft aquarium, for example, has a lot more surface area than a small fish bowl.

However…

When you agitate the surface water in your tank, the layer of water that is in contact with the air is constantly changing – the agitation increases the surface area of your tank, even though the physical dimensions of your aquarium are unchanged.

Surface agitation promotes gas exchange – the agitation increases the rate at which oxygen (O2) dissolves in water. It also increases the rate at which carbon dioxide (CO2) is released from the water.

Surface agitation promotes gas exchange – the agitation increases the rate at which oxygen (O2) dissolves in water. It also increases the rate at which carbon dioxide (CO2) is released from the water.

The amount of oxygen in your aquarium plays a major role in determining how many fish you can keep in your tank.

You need enough oxygen to keep each fish alive! The more oxygen in the water, the more fish you can keep!

Surface agitation allows you to keep more fish in the same-size tank.

That’s a pretty convincing argument for surface agitation, huh?

Even if you are not planning on stocking any more fish, there is another added benefit of surface agitation…

It gets rid of that oily film that appears on the surface of still aquariums.

You know, that oil slick that begins to form?

Well, the reason it isn’t going anywhere is because there is no water movement.

Agitating the surface water will help break up the oily film.

Is there such a thing as too much surface agitation?

In most cases, the surface agitation caused by aquarium equipment won’t cause any problems.

However, there are two instances when strong surface movement actually works against you.

1. Your fish

It may surprise you to learn that some fish hate surface agitation or any other water movement.

One of those fish is the Betta splenden (Siamese fighting fish).

I know that many fish stores keep their betta in a tank with an air stone bubbling away, agitating the surface of the water. But this stresses the fish.

In their natural environment, betta live in rice paddies and marshes – water that is very still.

To keep your betta happy at home, you want to replicate the gentle water movement found in its natural habitat.

So, read up on the preferred water movement of your fish before adding any surface-agitating devices.

2. Planted tanks

Remember how I mentioned earlier that agitating the water also increases the rate at which CO2 exits the water?

Well, for planted tank owners who are injecting CO2 into the water, that isn’t necessarily a good thing – you want the CO2 to stay in the water, not leave it.

If you are injecting CO2 into your tank, you want to reduce agitation down to a gentle ripple – so that you are not wasting CO2.

[Lo1]

Not all plants need Co2. Slow growing plants such as Java fern (Microsorium) and Anubias can thrive in low tech set ups. However, all aquatic plants will do better with Co2. This is because the dry mass of aquatic plants is 40-50% Carbon.

Since carbon is the major component of plant tissue, it will have the greatest impact, by far, on growth. NPK (Nitrogen, phosphorus, potassium) are important nutrients for plant growth, but they only make up a small portion of plant mass when compared to Carbon. A plant uses 10 times more carbon than all these other "macro nutrients" combined. This will give aquatic plants much better colour and healthy growth. The growth rates can be 5-10 times that of low tech aquariums.

Also, a much-overlooked benefit of CO2 is, that it gives rise to slightly acidic conditions that suit most species of fish that are likely to find themselves in a planted aquarium.

[Jon_D]

For the past 3 years I have had a planted tank, which is not heavily planted, (40 gallons I think) with plenty of healthy fish. The only agitation of the water is caused by the Fluval U2 filter and the plants are fertilised by the nitrogen released by fish poo.