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I have about 32 mid size cories in a 30G tank for about 5 months.
(Melanistius, Venezuelanus, Sterbai, Schwatzi, Zygatus, Pandas and Concolors, Sodalis, B.Splendens, C.Loreto, C.Surinamensis )

The tanks is filtered with Eheim 2215 with matured EHFISUBSTRAT in one compartment.
The temp hovers around 28-29 C. The tank has a year old 36W PL lighting.

The substrate is 1.5 cm of fine sand and some 2-3 mm gravel (different sides of the tank). I have 4 java fern /nanas on driftwoods that provides suff cover below mid level.
I've just added H.Difformis to add more shade and take up the ammo/nitrates. I change the water 30% every week. No test kits! Was hoping I can do without ...

I feed them once a day with some Hikari wafers and a cube of Hikari bloodworms - ensuring no overfeeding. They do eat well.

The Venezualanus (not wild) are the most adventurous lot going round the leaves up to mid level / upper part of the tank and sometimes 'surfing' against the filter outlet. The zygatus is the next most active. The rest laze around at the bottom and comes active only during feeding time. But zipping criss cross the tank no longer happens like when they were first added to the tank .

They are all very panicky when there is motion outside the tank, it does not help my working area is near the tank.

Question:

1. Are cories supposed to be an active lot swimming all over the tank or they are supposed to stay at the bottom? I've noticed the former behaviour only when the cories are first put in the tank.

2. Would an airstone help bump up the activity due non-feeding times?

They should be fairly active. If they are just staying still all the time, there's probably something wrong.

Mine are searching for food about the whole day, except for spawning now and then . Sometimes they rest a littlebit, but readily start to search the same spots over and over again.

I don't think I'm underfeeding them, as they are growing very well.

Hi Anthony!

Well ~30 corydoras in such tank is rather a lot.
What is the water T°?
With such number in that tank, you must have a good filtration, which in your case is rather good, but how much water do you change and how often.
Secondly have you check the water parameters values, such as nitrates, nitrites, ammoniac...
What about the lightening as it seem that your tank does not offer your cory many place to hide!!!
Cheers
Yann

looking at your list of Cory species you have some that prefer cooler water some that like it warn and a couple in the middle. So two questions what is the temperature of the tank and which species are the most active.

Ian

Anthony wrote:The temp hovers around 28-29 C. The tank has a year old 36W PL lighting.


Question:

Are cories supposed to be an active lot swimming all over the tank or they are supposed to stay at the bottom. I've noticed the former behaviour only when the cories are first put in the tank.

Since you added a little more info and since I have bought a new species yesterday, I can give maybe some input here.

About the temperature: I think that's pretty high! I don't know all the temperature ranges for all Corydorases, but this seems to me far to high. Even with the more tropical species, 26 degrees celsius will probably do. I keep panda's at 22-23 degrees (together with paleatus, for which this temperature is probably the highest they should have)

About the activity in the beginning: I observed that indeed my new cories (panda's) are really swimming up and down the tank walls, but I don't think that is normal. It might just be some stress from a new environment. This behaviour also remindes me of the introduction of the paleatus in the beginning. They were probably constantly looking what's going on above the water, and if it would be safe to 'take a breath'. My pandas, however, are really doing this at one spot, but it's getting less and less. I think that's normal.

Your Cories should, I think, be fairly often searching for food at the bottom, if not most of the time, and now and then check the plants as well (but that might depend on the species as well).

I currently have 6 3 lined cories, and just got 7 gold green cats (meleonotia sp???). The 3 line cories have always been active on the bottom but do rest when they can. They almost never go to the top to "gulp" air. However the gold green cats do all of the time. They are far more active (and skittish) than the 3 lined cats.


BTW (Tank is 100 gallon, with a built in wet/dry bio filter and a fluval internal filter with a spray bar......) temp is 76 F, 0 ammoinia, 0 nitrates, .25ppm nitrites. 30 % water change once every week.

From watching the cories activities I would deduce that there are distinct behaviours between the different types of cories.

Just my 2 cents!

SH

oh...pandas do not like temperature like 28/29....keep them in cooler waters about 23-24 degrees. NOt sure about the other species though.

That's interesting! I've been keeping my C. Panda's in 28 for just over a year now and they are fine. Or maybe they lifespan wont live longer in warmer water? I've herd this a while ago.