Okay I found something on them.
Turtle
Drops 180 Gold coins per 60 seconds. Has a gold cap of 250 coins
Drops Hermit Cat (Medium chance) Blue Giftbox (Very low chance) Pink Giftbox (Very Low chance)
Cost: 499 Gaia Cash. 299,000 gold in the Marketplace
Glows per 17: 3~9 (Unconfirmed)
1 Glow a day = 90 coins 90 x 34 = 3060/4 = 765 x 7 = 5355 x 42 weeks = 224910 gold in life span.
2 Glow a day = 180 coins 180 x 34 = 6120/4 = 1530 x 7 = 10710 x 42 weeks = 449820 gold in life span
3 Glow a day = 270 coins 270 x 34 = 9180/4 = 2295 x 7 = 16065 x 42 weeks = 674730 gold in life span.
4 Glow a day = 360 coins 360 x 34 = 12240/4 = 3060 x 7 = 21420 x 42 weeks = 899640 gold in life span.
5 Glow a day = 450 coins 450 x 34 = 15300/4 = 3825 x 7 = 26775 x 42 weeks = 1124550 gold in life span.
So after this would you still want a full turtle tank or something else? I'm just a very curious person.