i have a 10 gallon tank with 7 small cories (different species) and 2 ottos only. For the last couple of days, every morning when I go to turn on the lights, there's this big "hole" in the sand as if "someone" was digging and open a crater
Any ideas of who might be doing it and why?
also, someone told me this:
"when using sand,you have to stir through it on occasion as to not let bad aeromona pockets of gas form in the water because that could be deadly to a fish"
Not sure if this is what you were asking about, but deep sand will form pockets that do not have enough oxygen to break down waste-products (or anything else that may break down, such as wood, dead fish, etc). This is called Aneorobe pockets. Aneorobe breakdown is going to smell really horrible, because it produces, amongs other things, hydrosulpide and related chemicals [smells like well-rotten onion or eggs], and will be harmfull and/or poisonous to most oxygen-using creatures.
It's probably better to avoid this by making sure the sand is in a thin layer, rather than stirring it, as even with the best stirring, you're not going to get enough oxygen into the sand that way, you'll just reduce the amount of breakdown byproduct by releasing it into the surrounding area.
[Note: Aneorobic is the opposite of Aerobic. When someone goes to the gym for Aerobics, the purpose is to excercise at a level where the chemistry in the muscles has sufficent oxygen in the blood when producing energy, rather than aneorobic excercise which doesn't have sufficient oxygen levels, and therefore produces lactic acid (this is why it hurts in the muscles when you do certain really hard work, such as sprinting). A 100m runner will do almost all the running using aneorobic energy production.]
You're great! It's exactly what I wanted to know. The person who posted that answer (im sorry, but an idiot!) did so because my betta, who was in a tank with sand substrate died. I dont know what happened but she kept blaming my water params (which were perfect!!), making me feel like a poor fish keeper! Then, she made that point about the sand. Well, the amount of sand (deepness) is the same as the thickness of my finger. Have in mind that Im a woman and skinny!! After she said that I started worrying for the cories, but now im relieved.
If the cories are doing what they should be doing, and digging around in the sand for the food, then that would help prevent aneorobic breakdown, as it stirs the sand, adding oxygenated water in the lower sand-layers, as well as removing the stuff that would break down in the first place.
Half an inch or a little more is about the right thickness of sand.
Oxygen: an element that at normal room temperature is a gas, bound in pure form as O2 molecules. Atomic weight is about 16.0, 8 protons, 8 neutrons and 8 electrons.
Oxygen is what most creatures, from bacteria and fish to humans and whales, use to convert "fuel" to "energy" at cell-level. Also, burning for instance wood in a fireplace, will require oxygen to convert the carbohydrates of the wood into carbon-dioxide. Same sort of thing with the internal combustion engine in your car, fuel (petrol/gasoline) is burnt together with oxygen to form carbon-dioxide.
In the case of fish, they need to take oxygen out of the water, and in the cells of the fish, a form of sugar is converted (in several steps) to carbon-dioxide and water.
So for the fish to live, you need oxygen in the water. This is also used by the friendly bacteria that convert ammonia (NH3) to nitrate (NO3). As well, breakdown of organic matter, such as fish-poo, or any other "dead" stuff (wood, fish, bloodworms), etc, will normally require oxygen. If there isn't oxygen available, it's going to be an aneorobic breakdown, which will create "bad" things in the tank.
So oxygenated water is water that contains some oxygen. Oxygen RICH water will be water that contains a high level of oxygen.
So, in your tank, where the fish is happy, the water is oxygenated, because it contains some oxygen. When cories dig around in the substrate, they mix in oxygenated water from above the substrate that goes INTO the substrate, and help keeping the substrate free of aneorobic breakdown.
The amount of oxygen water can hold is dependant on the temperature of the water, the warmer the less oxygen.
