Let's throw another on the fryer!
Fish, Subterranean, Iridescent Plecos
Looks pretty straightforward.
Tiny Animal (Aquatic) that carries a disease.
We should do a Swarm version as well, but I'd stat an individual first.
I'd base the stats on a rat, but give them a higher Charisma 'cause they's so pretty.
Str and Con damage for the disease. I'd give it a racial bonus to its DCs. +4 seems too high, so I'll go for +2 - the swarm version will have a better DC with its disease, due to having more HD.
How's this for a start:
Fish, Subterranean, Iridescent Plecos
Tiny Animal (Aquatic)
Hit Dice: 1d8 (4 hp)
Initiative: +1
Speed: Swim 30 ft. (6 squares)
Armor Class: 13 (+2 size, +1 Dex), touch 12, flat-footed 11
Base Attack/Grapple: +0/-11
Attack: Bite +4 melee (1d3-3 plus disease)
Full Attack: Bite +4 melee (1d3-3 plus disease)
Space/Reach: 2½ ft./0 ft.
Special Attacks: Disease
Special Qualities: Superior low-light vision, scent
Saves: Fort +2, Ref +3, Will +1
Abilities: Str 4, Dex 13, Con 10, Int 1, Wis 12, Cha 7
Skills:
All ranks in Spot?, Swim +9
Feats: 1 plus Weapon Finesse (B)
Environment: Any underground aquatic
Organization: Solitary, outbreak (2-20), school (10-100), swarm, or plague (2-8 swarms)
Challenge Rating:
1/3? [Less tough than a Dire Rat but nastier disease]
Treasure: None
Alignment: Always neutral
Advancement: 2 HD (Small)
Level Adjustment: —
Disease (Ex):
Iridescent fever—bite attack, Fortitude DC 12, incubation period 1d3 days, damage 1d3 Str and 1d3 Con. The save DC is Constitution-based and includes a +2 racial bonus.
Skills: An irrdescent plesco can use its Strength modifier or its Dexterity modifier for Swim checks. A plesco has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.