Overstock Question

[James77]

How over stocked can you be and still make it work?

[rich311k]

Why would you want to be? I guess it would depend on the types of fish and the dedication of the aquarium keeper. I prefer under stock tanks, makes for much nicer fish and far more margin for error.

[Zilla]

I agree with Rich.

Aside from possible water issues, I personally don't like tanks that are really busy whether it be with fish, tank decor or both. My vanilla palette can't take it so I don't do it.

[tanks4thememories]

How over stocked can you be and still make it work?

No offense, asking that question means you most likely shouldn't try it.
A home aquarium is a balancing act of many factors. Just to name the main few.:
The number, size, and metabolism of the fish you keep,
Filtration,
Surface area of the tank,
Available space in the strata of the tank that the types of fish you keep, inhabit (Bottom, Middle, Top),
Feeding,
Aeration,
Temperature,
Enviornmental stress,
Temperment of fish.
Interrelationships between different species
All of the above plays a huge role in the health and longevity of your fish in a Home aquarium.
When you ask people or search online about the capacity of a given tank size. The formulas used to calculate the proper capacity are basically templates to build in a certain level of safety to allow for mishaps and mis- calculations and things that there simply isn't enough time to explain properly to someone who possibly isn't familiar with this balancing act called the home aquarium. As with any "Cookie cutter" formula you can bend the rules. However before you can do so with any hope of success, you need to completely understand the relationships between each of the factors I listed above. You just might find that by the time you do fully understand the above principals you will no longer even want to overstock... - Which is the meaning behind the opening statement, and the reason many people have several tanks.

[smaug]

Too many variables.Tell us your tank conditions with all parameters layed out,tell us your stock list at the moment and give us a rundown of filter size,plants,decor and your experiance level and we can help.Dont worry we will be nice about it.

[Dacotah7]

Using the fresh water stocking rule of thumb, 1" of fish per gallon of water, you are heavily stocked now.

Quantity - Species - Adult Length = Total Length
5 Rummynose Tetra's X 2" = 10"
5 Cherry Barb's........ X 1.5-2" = 7-10"
3 Rabauti Cory's....... X 2" = 6"
3 Otocinclus cat's..... X 2" = 6"
1 Redtail shark.......... X 6" = 6"
GRAND TOTAL....................35-38" Total Length of Adult Fish

35" / 20 Gallons = 1.75 or 175% Stocked
38" / 20 Gallons = 1.90 or 190% Stocked

Your 20 gallon tank likely does not have a full 20 gallons in it. It is not filled to the very top edge, and likely it has things inside it that displace some of the water, including substrate, rocks, equipment, plants (plastic or live), or ornaments. Just a little water missing is significant. If you actually have 18 gallons of water the revised calculations are:

35" / 18 Gallons = 1.94 or 194% Stocked
38" / 18 Gallons = 2.11 or 211% Stocked

Some of your fish in that environment may never attain their full adult length.

If you do not have plants, consider:

Aquarium setup:
SOURCE: http://www.aquaticcommunity.com/fish/common/o/

Hemigrammus rhodostomus (Rummy Nose Tetra) should be kept in a well planted aquarium with a lot of free swimming area in the center of the aquarium. They can be sensitive to rapid changes in the water conditions. Hemigrammus rhodostomus (Rummy Nose Tetra) should only be kept in schools.
Company: Hemigrammus bleheri (Rummynose Tetra) is suitable for community aquariums.

Barbus titteya (Cherry Barb)Are very timid and more peaceful then most other barbs. They prefer an aquarium with a lot of vegetation with some open areas to swim on. They should only be kept in schools of 6 or more fishes. ~ NOTE: You have 5 now. ~
Company: Barbus titteya (Cherry Barb) should only be kept with other small species.

Otocinclus Catfish can be kept in quite small aquariums. They prefer a well planted aquarium and should be supplied with plenty of hiding places. Hiding places can be created using roots and rocks or by using bought aquarium decorations. Otocinclus Affinis (Oto) prefers a dark bottom sustrate.
Company: Otocinclus Affinis (Otocinclus Catfish, Oto) can be kept in community aquariums with other small species.

Red tailed shark - Epalzeorhynchus frenatus
A large aquarium, heavily planted, with plenty of hiding spots for it to claim its territory.
Company: Other semi aggressive fish. Two fish of this species should not be kept in a tank to keep aggression at a minimum.

~ * ~
But you probably already knew all of this, prompting your question.

If you are thinking about adding more fish, think again. Consider another tank or a larger tank. Do it right. Yes you could probably stuff more in your tank, but the fish may feel stuffed in there. Consider their qualitity of life.

The professional advice is your fish want plants, your barbs would be happier with one more mate, and the Red tailed shark belongs in a large tank. Most do not consider a 20g a large tank. Yes, next to a gold fish bowl or a 5g it looks larger, but I think of a 20 -25 at the upper end of small tanks.

[gm72]

I agree with all of the above posts, very well done.

Let's get away with the 1" rule however. There is no rule to stocking. A 4 inch loach does not carry the same bioload as another 4 inch oscar.

There are simply too many other variables.

[VoidParadigm]

If you go by bioload and space instead of the poorly used 1 inch per gallon "rule" the OP's tank is only about 110% stocked.

In any case, how much you can overstock is based on many different variables, including but not limited to filtration, plant material, aeration, maturity, aggression of species, and so forth. Hardiness as well; guppies for example can be in much closer quarters healthily than many other more fragile fish.

[Crispy]

There will always be those who push the envelope. I am overstocked, but it's taken me many years and much trial and error to pull it off. But it can be done. All my assorted fish in my sig live happily together.

But getting the right mix and the fish you want is no easy task. You'll have to start deciding on some of your 'centerpiece' fish and build around them for starters. Some, like loaches, will take a long time to grow. I started growing out my fronts and loaches years ago knowing someday I will add an arowana. There are a million factors here depending on your vision.

[James77]

In about a month I will have a 55 gallon to transfer all my fish into.