Most things from the wild need something (fish, bird droppings, copepodes...) to introduce the disease to the snails before they can introduce them back to the fish. There are very few seagulls flying around our house. ;)

(A sparrow or two and a starling got goofy perching on the flu and fell in the house though.)

Having said that, in a disasterous tank, snails and plants (unless the plants are really valuable and merit a separate soak) are pitched. Even have dumped some gravel in the garbage. (Gravel from hopelessly hair algaed tanks goes under the stepping stones in the garden.)

If the fish, plants and snails are in a treated tank, they are kept. Obviously snails from a "sick" tank could carry the moble forms of ich or velvet in the water accompanying them. If their tank has become rid of the malady, my hope is that they are no longer in contact with them.

If someone knows of specifially snail carried diseases in an aquarium, I too would like to know.

If you have a grimy spot in the gravel where the fry food falls, you do want to siphon that out. That waste material is the biggest threat you have right now to your fry.

By the way, if fungus is growing there, that is nature's way of cleaning up the mess. Unsightly, but maybe a step in the right direction. Still you want to siphon all the fungus, which will be clinging to as much food as it can. Also get "all" the stuff under the gravel. While a modest amount of organic goodies do stratify at the top of the tank, the biggest concentration of gunk is at the feeding spot.

Your concern about siphoning out fry suggests that you need to get a gravel vacuum. Ginger. Lee and others make some fairly inexpensive models. They are essential for getting debris which is sifting down into the gravel.

Almost made some smart alex remark that if you were concerned about fry getting sucked up, get a smaller hose. But you know what? Get a smaller diameter gravel vac (or gravel grunger).

There will be a trade off in terms of a little longer time pulling water from the tank. Smaller ones will be less expensive though.

Once took a small diameter length of plastic tubing and attached it to the small end of an old turkey baster tube. Cheapskate city, but just right for tight quarters.

I wish that so many questions weren't met with responses involving spending money. I'm imagining
what one of those vacs would look like sticking out of a Christmas stocking. ;)

If the fry are eating the sun dried shrimp or the paste and they are growing, stay with them. There are aquarists, blender in hand, who make their own paste foods and food mixes. Do a google search or go to the Krib for more. There are so many commercial foods and culturable live foods that most aquarists don't take the time to make their own. (and many of the food mixing people have blenders on their holiday gift lists.

Home made pastes have to be fed carefully too though. The size of their particles means they can get spread around easily if not eaten.

Frozen foods are probably more expensive than any other kind of fish food except live foods. They are good for growth and conditioning breeders. Neither are absolutely necessary. Most aquarium fish can be very well maintained on a variety of flake or pellate foods (depending upon the fish size). The meaty stuff does give a boost though. (Does your dog prefer kibbles or ground beef?)

Probably not an issue with yours, but be careful not to defrost and refreeze those frozen food packages if you do get them. In fact, don't buy any packages which have obviously been defrosted and refrozen.

Food animals split open may lose nutritional value and increase the gunk in the defrosted food. (Gently rinse what was defrosted in luke warm water in a jar through a fine mesh net or seive with cool water).

In extreme cases, defrosted food can spoil. When it is used it can endanger the fish.

This time of the year, the wee bit of defrosting on the way home from the LFS is not a big issue. However if planning on buying frozen fish food, I will grab an appropriately size styro, plunk one of those frozen plastic covered gel refrigerant packages in there and roll. If live black worms or brine shrimp or (seasonally) glass worms are likely to be purchased, a section of newspaper will be included. The live foods are divided from the ice and frozen stuff by the newspaper.

Those six pack coolers from the summer work fine too.