Some considerations:
You want to feed your fish consistently. It is better to fill you fish with your #2 choice in food, than to feed them a little of your #1 choice but run out and leave them hungry. (Except for the weekly or biweekly fast.)

You can keep your guppies happy on just one good guppy food mix. However ...

You may also (even though a lot of flakes are a mix) want to give your fish an even better a good variety.

You don't want to go broke feeding them.

Rinsed frozen foods, especially for fish like guppies, who will forage all over the tank, are a wonderful substitute when live stuff is unavailable, too expensive or requires too much precious time to culture or care for.

If you culture stuff, you need to only grow what you can somewhat conveniently grow. I live in a house with a slab foundation. Summer heat makes it impossible to grow white worms or red worms. But I am lucky enough to have several cultures of Daphnia. Deciding what I raise is a no-brainer. I still swing by a local LFS every week or two and buy 2 oz of blackworms, which are rinsed and rinsed and then stored in the refrig, nestled a couple of those wonderful blue worm holders.

See
http://aquaticfoods.com/accessories.html
http://www.wetthumbaquatics.com/

But first, let's praise the flake food manufacturers for producing good products and continuing to tap into fisheries research and improving their products. Today there is not just one generic, one food fits all, product available. There are a lot of foods engineered and proportioned for specific (groups of) fish.

I too, would be really interested in what other GL people would recommend for prepared foods.

Your guppies are omnivores and need both animal and veggie material. Most tetras (as a part of the group of families known as Characins) are carnivores and especially fond of insects which fall in the water (and their larvae living in the water).

(There are two-three-foot long characins with fiercesome dentures, which feed on smaller fishes and are much sought after by fishermen too. Aren't you glad you don't have to feed them? :)

Your tetras makes me think of an unaccomplished project. I have some new surface feeders and wish I had taken an old landing net, which is lined with sheer curtain material. (Actually its most recent use was in getting cats out of trees.) Last night's frost may make this impractical now, but I have been really tempted to take that net and a couple of gallon pickle jars, with tops, and stroll down the road to a field which has laid fallow for several years (probably until the builders tear it up). When no one is looking, I intend to run all over the place, sweeping that net before me, stopping to empty it into the gallon jars. Hopefully a bug run can be made before neighbors start making phone calls and the men in white suits take me away. ;)

But seriously, there are a lot of flake and pellated foods and even freeze-dried floating foods of benefit for your fish. If they don't take them, you are faced with the choice of either switching foods, or if you think that the new item is really important, "fasting" or not feeding them for a couple of days until they try it.

Compare our foods today with the rice flakes (!) which in the 1930s and 40s and even into the 50s were sometimes all aquarists had to feed their fish. Amazingly, most fish survived and grew. No wonder though that aquarists went to forest preserves and swamps (now housing developments) to collect Daphnia!

Live Daphnia and the like are safer for the fish if cultured in your back yard. NEVER collect from waters where there are fish - the live foods can be vectors for fish diseases (Camallanus for instance) which would be virtually impossible to bring to the fish with stuff raised at home. Even pond collected daphnia and mosquito larvae may also include hydra and possibly predatory insect larvae.

While people, including the incomparable Rosario LaCorte (who used cardboard boxes among his culturing ingredients), have raised brine shrimp in a back yard barrel, it is a lot harder than raising Daphnia. (Please see my Daphnia link below.) Another advantage of Daphnia is if you overfeed it, they swim around, feeding on bacteria and algae until the fish eat them - they can remain for days! (Two months once here, cheerfully procreating, foraging and hanging out on the corner until consumed.) Brine shrimp do NOT carry a any of the diseases or pests which pond raised live foods carry, but if they die and are not cleaned up, their decomposing corpses seem to offer a great environment for a velvet bloom. (The velvet, like cold germs and taxes, were always there. They become a serious problem with the deteriorating environment.)

Please also check the quick link for Brine shrimp.

Baby brine is among the finest foods one can give to fry. The aquarium hobby and industry simply wouldn't be what it is without brine shrimp - especially the baby b.s. Live (within a few hours of hatching) is best. Frozen, if accessible to the fry, is very good. (They're loaded with those HUFAs.) As with all wonderful things in life, if we aren't somewhat moderate in what we do, there may be consequences.

As mentioned, it has long been the bane of killifish to get velvet. 99% of the time there was also an over feeding of b.s. and uneaten bodies lay on the tank bottom for over a day. At a certain point down the road - whammo!

It used to be that aquarists blamed the brine shrimp for being a vector for velvet. Several of us began to wonder though if it doesn't just set up an environment where the organism blooms. Former Shedd Aquarium vet Dr. Martin Greenwell tends to agree.

This is where having a pond snail infestation in a fry tank will be a huge blessing. (Even those much-loathed Malaysian livebearing snails have their uses - especially in guppy tanks.) People always tossing out snails, even killinuts, when asked if they ever have encountered velvet, will respond, "what's velvet?"  So don't clean all of those snails out of the fry tank!!!!

I've looked up a bunch of GL references and also a few other favorites of mine. It resembles the reading list for a community interest course at a local high school or community college. (Another project on the back burner.) Still, I hope it is useful to you.

See Quick Links for Brineshrimp

I know guys who have engineered their own brine shrimp hatchers for a mere $150. You can also spend a lot on a hatchery of your own. I probably have three or four of them around here. I still prefer using those pickle jars and hard tubing  mentioned in the quick link.

GL on Foods

Blood worms, Good News and A Caution
Care Tips
By unclescott
from the Foods department, Section Ask Guppylog
Posted on Mon Dec 8th, 2003 at 14:26:44 PST

Guppy Fry and BBS Alternatives
Care Tips
By Timbers Guppies
from the Timbers Guppies department, Section Ask
Guppylog
Posted on Sat Jan 31st, 2004 at 23:18:35 PST

Diet and Defaecation    
All Topics
By miskairal
from the miskairal department, Section Ask Guppylog
Posted on Tue Jul 6th, 2004 at 20:56:13 PST

Feeding The Fry & Adult Guppies
All Topics
By erdemozkan, Section Ask Guppylog
Posted on Sun Oct 19th, 2003 at 11:49:13 PST

Mossie Eggs Already
Care Tips
By unclescott
from the the live foods department, Section Ask
Guppylog
Posted on Fri Apr 2nd, 2004 at 11:44:55 PST

Blanched Blackworms and a Look at Pecking Orders    
Care Tips
By unclescott
Posted on Sun Apr 11th, 2004 at 17:05:51 PST

Garlic is beneficial    
All Topics
By maggie1270
from the Maggie department, Section Diaries
Posted on Sat May 1st, 2004 at 09:37:48 PST

Peas Please    
Care Tips
By unclescott
from the Dietary Considerations department, Section Diaries
Posted on Tue Jun 1st, 2004 at 12:45:50 PST

Feeding Care    
Care Tips
By MimiGuppy
from the MimiGuppy department, Section Ask Guppylog
Posted on Sat Sep 25th, 2004 at 23:12:54 PST

Guppies gone Quiet
Behavior
By miskairal
from the miskairal department, Section Ask Guppylog
Posted on Tue Sep 14th, 2004 at 04:16:33 PST

http://guppyz.tripod.com/fish_food.html

Another great site listing page:
http://www.cbel.com/freshwater_fish_and_aquaria/

This is one of my better Daphnia posts. A Google search for Scott Davis and Daphnia will get you too much chaff.

http://www.thekrib.com/Food/daphnia.html#19

Two useful archives:
http://www.thekrib.com/Food/brine-shrimp.html
http://www.thekrib.com/Food/daphnia.html

http://fins.actwin.com/live-foods/
is a mailing list. I've been a member from time to time. The Krib has a searchable archive.

I am dismayed to see that the still useful archive stopped in 2002. Thank you for reminding me to rejoin. I'll try to find out what happened to the archive... sometime. ;)