Contrary to common myth, the offspring of hybrids do not "revert" to one of the parent species. The offspring of hybrids contain a greatly varied mix of genes from the two parent species, so that some offspring may resemble either parent species, while some look more like the original F1 generation of hybrids.
If your BGxGSF Fx offspring end up all resembling GSF, you are likely managing your pond to encourage fish with mostly GSF genes over over those with mostly BG genes.
| 
