Tavo, for your goals here is what I would do. I have only been actively managing a pond for three years so my advice is probably wrong, so keep that in mind. But my opinion, for what it is worth.
You have already got GS in there. They can be a problem or an asset, depending on how you look at it. I can not tell by the pictures how big the GS are, but it looks like they are fair size. If you have 5 or 6" GS in your pond, anything like BG or HBG you stock that are only a couple inches long are likely to only become expensive fish food for the GSF. I have GSF in an older pond of mine and have recently introduced a few in my main 3 acre pond (after the BG were well established). They are very aggressive fish and are fun to catch for kids.
But I digress. What I would do in your situation and for what you want as results is simply go out this spring and find a place you can catch about 10-20 male adult BG off the nests and put in your pond. You need to make sure they are male only (no females to reproduce). Catch some 6"+ ones. Being male only, they will readily make nests and reproduce with the GSF females in your pond. You will have your own redi-made HGB population.
If you buy HBG (which is what I also think will fit your situation) that are 1-3", few are likely to survive the already established GSF in your pond. The bigger GSF are going to eat them. You could buy larger HBG fish (at a much higher cost - if you can find them). But why not let the GSF females do the work and produce your HBG for you? Just add adult male BG and let them do the work for you. The down side is it will take a year or two extra compared to buying and stocking advanced size HBG.
If you make a mistake and accidentally get one or two female BG in the mix, it will not be the end of the world. It just means eventually the BG may get the upper hand on the GSF and you might have to add some predators to control them. You are going to need some thing to control the GSF population anyway. By introducing some male BG to cross with the GSF, a large majority of that cross offspring will also be male, filling the biomass in the pond with a slant towards heavy male. This also might help with population control to a small degree.
My idea, for what it is worth.
Edit: I would also add some RES for snail control. They would need to be big enough size so the GSF will not eat them though.
Last edited by snrub; 03/17/16 10:00 AM.
