You sound pretty familiar with the technical side of the hobby and the kids would be pretty safe with fish. I remember reading cautionary tales of kids trying to do water changes around electrical outlets and so on. We took those stories very seriously. Actually the worst side effect among my friends was when some filter floss got flushed - well part way - and that stunt was pulled by an, ahem, adult. ;)

Are the Aquaclear filters a Hagen line with pretty good water movement? I can see why you would keep fry segregated. I have heard of people taking an additional long extension tube and drilling all sorts of small holes in them to dissipate the pull of the current. I don't know if that would work, even if an elbo was put in the drilled tube and it was run the distance of the tank side.

Your fry are probably best served by a sponge filter. If you have a box filter in the closet, those work well with fry. Maybe use it with a full bed of floss and the box filter top removed. I've even seen people stick one of those little u.g. filters for bowls in a bowl of gravel - an inexpensive way to recycle old gear but maybe not as efficient as a sponge filter - with it's surfaces and rotifer cultures all over.

Would your sucker fish be Otocinclus? Those are great algae cleaners and safe with most fry. (Not eggs though if you work with egg layers.)

The drawback to the Otocinclus (there are a bunch of "Otos" although we usually only see a species or two imported) is that they are usually wild fish and I found out to my sorrow they may bring catfish diseases with them. Rather than quarantine a batch given to me as a present several years ago, I plunked them in a community tank and soon after lost a number of very large Corys and some 8 year old bristlenose "plecos" Also, as you probably know, new ones can be touchy, maybe because they are so hungry.

You may be very familiar with this, but if they clean all the algae off, pick up a zuccini, blanch it or quickly zap it in the microwave. Cut it in slices and freeze what you don't immediately need. Most suckermouths or Loricariids do well on zuccini if you don't want to purchase the usual sinking veggie tabs.

At any rate the Otocinclus are benign around fry where (as per Guppy Girl's warning) the so called Chinese algae eaters (a.k.a. Thai slime suckers) will be trouble.

It isn't standard procedure, but I've seen guppies being bred in the same tank where dwarf bristlenose "plecos" (Ancistris species) were also being bred. They occupy largely different nitches from the guppies. Baby bristlenoses may even be added to guppies with the assumption that they will clean up uneater baby brine shrimp. I would add them just because they are cool little fish. And the guppies will browse the algae tabs.

Are your walking fish the "climbing perch" Anabas testudineus? I recall an interesting article somewhere where experimenters had them climbing little ascending walkways. They have proportionately big mouths.

An irrevocably final culling fish is handy.