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assuming i'm not having any fish in these tanks besides cories, how many would you recommend i keep in 1) a standard 10 gallon tank and 2) a 20 gallon long tank?
-Liz

What dimensions are the tanks?

Jools

Let's see, a standard 10-gallon would be 20" by 10" by 12 1/2" (length X width X height).
A 20-gallon long would be 30 1/4" by 12 1/2" by 12 3/4" (length X width X height).

What are the surface dimentions of both tanks??

Ian

Bathos,
These questions are really tough to answer as there are so many factors to take into account. For example, the answer would be different for C. barbatus and C. habrosus. It also depends greatly on what type of filtration you will have and how often water changes will be performed. You could keep 35-40 C. aeneus in a 20 long if it had a big sponge filter and you changed half the water every day. The same tank with a smaller filter and only weekly water changes could only hold 1/3 as many fish. I do not believe in any type of "so many inches of fish per gallon rule" as neither the inches of fish nor the water volume are what matters most (they also do not take into account fish mass i.e. ten Neons or a ten inch Oscar). What matters most is the quality of water filtration and how often the aquarist is willing to do water changes. Wholesalers here will keep 75 Corys in a 20 gallon tank, but the tank has a huge sponge filter and gets 80 percent water changes twice a day.
I think the best way to determine stocking levels is to first decide what type and how much filtration you will have and how often you will really have time to do water changes.
Jack Wattley has done some neat experiments with regards to this issue and his findings were very interesting. 20 Discus fry in a ten gallon tank will outgrow 10 Discus fry in a twenty gallon tank if the 10 gallon receives twice as many water changes as the twenty.
Something to keep in mind.
-Shane

I'm not quite sure what you mean by "surface dimension". If you are referring to the surface area available for the fish to swim in, isn't that just length X breadth?

Surface area should just be length X width as you said Silirus. How much oxygen the tank receives, of course would be decided by how it is areated.

Speaking of that should you have a air pump in ones tank if it is deep (ie 24" or greater) or will a spray bar and powerhead be sufficient for surface agetiation?

PS is there any way to measure oxygen in the tank?

SH

PS is there any way to measure oxygen in the tank?

You can either use a chemical analytical method (which means you scoop some water out and use a bunch of chemicals to test DO levels) or use (an expensive) DO meter.
Either way, it's not simple/cheap.

I was looking for a starting point related to 3 sq inch of surface area to 1 inch of fish (body length). Airation, filteration and water changes are all ways of stretching the natural limits. Lets walk before we run.

Ian

LOL.. good point! mmm... 3-1 ratio of surface area to fish. Sounds like a good method to start with. (already getting the calculator out...)


SH

sorry, got stuck in Boston due to snow.

i'll check on the dimensions tonight. i'm pretty sure Silurus' measurements are correct.

i'm most interested in C. trilineatus at this point. i'll probably expand my cory collection to include similarly sized cories. i don't think i'd get anything larger than C. aenus.

filtration on the 10gal is a whisper 1 and on the 20gal long it's a whisper 2. i'd like to add some sponge filters to both tanks, but it probably wouldn't be anything real high powered.

water changes are currently 25% weekly. wouldn't want to do much more than that on a permanant basis.

35-40 adult cories sounds like way too many for a 20gal. i'm worried about being crowded with 6! (5 C. aenus, 1 C. trilineatus) i want my fish to have room to swim, but i deffinately want to have more cories. how many would you keep in those tanks? how many could fit in the 20gal long without "stretching the natural limits" (to quote Ian)? how many with the filtration and water changes i currently have?
-Liz

Bathos

I will go back to my original point. I have stock tanks in my fish house that hold about 18 gal (imperial) but the tanks are 18" wide 36" long and 8" high. The surface area is 648 square inches divide by three equals 216 inches of fish for the surface area. The average Cory in there is 2.5" this means that I should be able to house 86 Cory's in each tank, there are actually around 50, so I have room to spare. there tanks are filtered with Fluval 204 outside canisters and internal porpose made partial undergravel units.

I try to stick with the 3 square inch of surface to one inch of fish so in the case of power cuts and the like I am confident that the fish will be OK.

Ian