I make 1 cube last 4 days, according to Frank of Frank's Tanks for my two clown fish.
Here's how:
1. Allow the cube to unthaw. Does it still look like a cube or is it a melty mess?
2. If it still looks like a cube, add 1-2 tablespoons of tank water
3. If it is a watery mess add 1 tablespoon of tank water
4. If you can, add Kent Fresh/Marine Garlic Xtreme per the directions (for their immune system; infections, ect. (I paid $16.99 for a 1 oz. bottle with dropper (but little is used per cube)
5. If you feel like your fish potion is still a bit thick, add one more tablespoon of tank water and stir around.
6. What I have not perfected is finding the itsy bitsy ice cube trays--maybe Michael's or Hobby Lobby has them. Then divide the potion into 4 ways; you can pour it into the corners of 4 Ziploc bags and freeze them
7. Each feed, run the frozen bit under hot water, which dethaws it, and you are ready to feed.
**Warning to myself and to all newbies: As a neonatal nurse, I can share with you that a newborn's tummy on day 1 of life is as big as a marble. Compare even a 500g baby's tummy (a micro-preemie's) to the size of your small fish's and realize that their tummies are nano-tummies!! We want to overfeed because we see their zeal to eat; but, they don't have all the neurons and hormones to say, "I have had enough". Okay, that's too much!