I'm almost positive that E variatum is an egg burrier. No nest, they just
shimmy down into the gravel during the act. Males may choose and defend
prime areas defined by substrate type and water flow conditions. If you
really want to save the fry, I would take out the adults as soon as you
think they have spawned. There is a few days time before the eggs hatch,
so that gives you some leeway. They do not guard the fry. Any baby
darters in the tank with adults will quickly become a food item. If you
want hiding places as a backup, you need small enough spaces that the
adults can't squeeze in or are otherwise detered. I think Java moss or the
equivalent might work. But the fry aren't smart enough to avoid danger
until well after they start taking on their adult-like form. Yeah, maybe a
layer an inch or more of the large stones would act like marbles and form
small spaces that the adults can't penetrate. They may not like that as a
spawning substrate, though, so there should be lots of other areas with the
finer gravel. If you use an undergravel filter, definitely use the _fine_
red flint, so the hatchlings won't be sucked down through the gravel. I
have done this successfully with darters and minnows. It resolves the
issue of the filter intake, since the entire gravel bed is a filter intake
and the flow is dispersed. A stardard power or canister filter intake
would efficiently filter all or most of the fry out of the tank. Fine-pore
sponge filters should be OK.
Mark
Ohio
USA
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