To go with KNGZRO's report above, many of the exchanges seem to accept only PART of an option. I have Moss Mutant Crabs, and this is what I see:
But if I stick all but a few of my crabs into a trade so that they aren't available, I get the same thing KING does, only I have more Green Striper, so I could make more:
When I get my Moss Mutant Crabs back, I see the first image again. As such, this means that the exchange is somehow treating each piece of the exchange as a viable one, instead of requiring all necessary pieces in collaboration. I tested this glitch on the 4x Bluestone Helm, an item added in the 2006 update, and it still works properly. That is, if I remove enough fish of one type from my inventory, the option to make the item disappears, so it appears to be an issue only with the Aquarium fish exchanges, unless having multiple options is affecting this. We don't have a lot of exchanges with multiple options that also require multiple ingredients, so I can't be sure which is the point where the glitch enters in.
*Sidenote: While testing these things, I found that I cannot take game items out of a trade; I must instead cancel the entire trade. Very irksome.
I can also confirm that it is consistent across Aquarium Fish exchanges added on January 27th by experimenting with the Aquarium Lazor Fish [lite]. Below is my view if my inventory is "unobstructed":
Then, again, I put enough Acidic Jellies into a trade so that I do not meet the 25 requirement, and this is what I see:
This also raises the concern regarding 3 part exchanges. These and others may require more than we can see, and it's simply allowing us to exchange for any of the parts as opposed to needing all of them as it should.
Also, there is the Aquarium Ninja Fish [lite] exchange. See below:
As you can see from the image, there is one exchange for 100 Black Pebbo Feeders and 25 Black Rocque Biters. However, the next one down is 100 Black Pebbo Feeders and 5 Black Roqcue Biters. This may be another instance of the glitch detailed in the first two cases, but as it stands, the exchanges are not only redundant, but one is obviously less worthwhile than the other.
Edit: It seems that I've found another glitch. According to reports and such that I've gathered, these are the following exchanges for Aquarium Watermeat [lite]:
Exchange Option 1: 50 Blue Seedkin + 20 Kohaku Koi + 5 Blue Striper
Exchange Option 2: 30 Kohaku Koi + 30 Electric Jelly + 20 Russian Catfish
Exchange Option 3: 200 Blue Seedkin + 50 Blue Striper + 150 White Pebbo Feeder
I qualify for the 1st and 3rd options, but I cannot see the Watermeat [lite] exchange.
Likewise, the Aquarium Starfish [lite] exchange list appears to be the following:
Exchange Option 1: 250 Yellow Guppy + 25 Cool Rainbow Trout
Exchange Option 2: 35 Peach Balloonfish + 25 Sulfuric Jelly
I qualify for the 1st, but cannot see the Starfish [lite] exchange. It appears that there's something requiring the user to meet a specific option's requirements before they can see any of them.