First of all, let's determine how many sticklebacks we actually have in the pond. Since it's given that one third of the total fish population consists of sticklebacks, we divide the total fish count, which is 30, by 3. This give us 10 sticklebacks.
Next, we need to find out the quantity of tench. As per our information, the pond only has three species of fish: carp, sticklebacks, and tench. The carp count is already known; it's 9. We also found out that there are 10 sticklebacks. So, to determine the amount of tench, we subtract the number of carp and the number of sticklebacks from the total fish count. This is 30 - 9 - 10, which equals 11. So, there are 11 tench in the pond.
In the last step, we must calculate the ratio of sticklebacks to tench in the simplest form. Given that there are 10 sticklebacks and 11 tench, the ratio would be 10 sticklebacks for every 11 tench, which can be written as 10/11 in simpler terms.
So, the ratio of sticklebacks to tench in the pond is 10:11, or 10/11 when converted into the simplest form.