Something REALLY odd going on with cory(?) eggs

[Becki]

Well, A bit ago I decided to move my habrosus to a tank I have set up for spawning my otos, to try to get the cories to spawn, and then move them back to their regular tank, and move the otos IN to the hormone-filled water, to hopefully induce them to spawn.

After a couple of weeks, I wasn't having much luck with the cories there (I had bred them before in the other tank), so I moved them back to the tank I had previously bred them in, hoping there was SOMETHING about it they liked better.


Either I'm blinder than a bat, or something REALLY funky is going on. Within an hour-(less, I think) I came back and noticd literally hundreds of eggs on the plants (I have 7 female habrosus, 5 male). They were like wallpaper on the underside of many leaves, crammed in right next to each other. When I had spawned them before, it was nowhere near this prolific or sudden. Plus before there was a greater ratio of eggs that were placed on the glass, all eggs except for about 8-12, in one cluster on the glass, were on the plants.

I didn't test for hardness, but it should be about the same as I clean out both tanks at the same time. The one with the dark gravel that I couldn't get them to breed in is a 15 gal, with co2 added. The one they loved is a 10 gal, no co2. Both have plants of the same species, no other difference I can think of besides the one they didn't like had dark river gravel, the one they loved had light river gravel. (could gravel, or rather the brightness of a tank due to light reflection vs absorbtion, affect breeding, or could the level of co2?)

The habrosus have spawned today, leaving eggs in the fashion I had seen them do before. These eggs are bigger than the eggs that were laid over the weekend. The eggs I found this weekend are 1/2 to 2/3 the diam. of today's eggs. (Sorry, I don't have anything with increments small enough to tell you what size). The weekend eggs starded hatching last night, and I have somewhere between 150-200 fry, and only a couple of casualities so far over the last 24 hours. The eggs from the weekend weren't 'tacky' in the same fashion as the ones I had dealt with before and since, though even several days after being laid some still are nearly inseperable from those next to them, unlike the eggs I've dealt with in the past that loose their tackiness after a while.

Offhand, I'd have to say that the eggs would more likely be from the previous inhabitants. If it weren't for the fact that there were just so MANY of them sticking out like a sore thumb, and the fact that i had to remove the plants from the tank to catch 'em all (you think I'd notice THEN, for sure!), I'd be 99% sure it was someone else. The previous inhabitants were bilenateus (San Juan) cories and zebra otos. I'd find it hard to believe (though I guess not impossible) that the larger cories would produce smaller eggs, or that it was my zebra otos (I don't know if I dare to dream...)

I know that environmental factors could influence the size of eggs, but this whole situation seems downright odd. Could co2 (the only real environmental factor besides quantity of light) affect egg size, when the adults were kept in a tank with co2, but the eggs laid in a tank without? The next few days should rule out if they are oto fry or not, but it'll take longer to determine which cory they truly are.

Thanks for any help you might have!!

[MatsP]

Any factor, colour of the substrate, plant selection or CO2 could affect the behaviour of the fish. Don't think it would affect the size of the eggs, but I don't know that.

I'd have to say that CO2 is probably the most likely factor. CO2 will change a lot of things, but most importantly it will affect the "breathing" of the fish, just the same as it affects our breathing (our lungs have a CO2 "sensor" that is causing us to breathe, higher CO2, heavier breathing).

Of course, a fish that is "out of breath" will not be particularly keen on spawning...

That's just my thoughts on this, and I could be horribly wrong (it wouldn't be the first time).

--
Mats