I tend to agree that creating a competitive feeding scenario would be your best bet. If the carp are competitively feeding in earnest and in numbers and they are larger than the other fish they will muscle the others out and you will achieve your objective of catching more carp than other fish.
Since it appears that scent plays a large role in your ground baiting style in SA you could try the traditional groundbait recipe used here in Bangladesh. It works!
Find an Indian grocer or spice seller and buy the following:
Fenugreek: whole or powdered 1lb
Sweet flag: whole or powdered 1/2lb
Nutmeg: whole or powdered 1/2lb
Lesser Galangale: 2lb
Spice Pages: Lesser Galangale (Kaempferia galanga, kencur, Sand ginger)
This last is usually sold by Indian spice merchants but you may find it easier to source from a Chinese supermarket. You can get it online but expensive. The link above will help you find the English and other names for the various spices and any others you may fancy in the shop.
You can vary the quantity in the ratio above. The critical ingredients are Lesser Galangale and fenugreek. The other spices are optional but the more the merrier.
If you get the above in a powdered form then well and good. Mix it all up and keep in a wide mouthed stoppered jar or two. If however you have got them whole then partially roast these on the end of a shovel or on a frying pan outside somewhere until the aroma can be smelt at a distance of eight or ten paces! Then while still warm grind them up in a mortar or grinder to a fine powder, mix and keep in a stoppered bottle as above.
You are warned to do the above outside or in a garden shed otherwise the aroma will drive you from your house or your wife will! The stoppered bottle should be WELL stoppered for the same reason and the mixture is best kept in the shed. It is not an unpleasant smell, just overpowering.
Get about 10kg or so of mustard (rapeseed) oil cake. The Oil cake should still have a mustardy smell to it. However modern mills are exceptionally efficient and will squeeze the last drops of oil out leaving an earthy smelling cake. In that case, add a small quantity of mustard oil to the cake (supermarket should have it). Make a fifty fifty mixture of water and sugar and reduce it by boiling till it is really syrupy. Break the oil cake into small (half a palm size) pieces and put it into a plastic drum/ bucket with a lid. Add the syrup to the oil cake and let it soak in. Do this a small quantity at a time until the oil cake is the consistency of damp clay or a softish paste bait. Be aware that the oil cake will significantly increase in volume as it soaks up the syrup, so leave enough room in the container and keep the lid on while soaking. Otherwise you will have maggots in the oil cake paste (not that that stops attracting the fish!). If the mixture is too runny add dry oil cake until you get the right consistency. You can also get powdered oil cake and this works just as well and soaks up the syrup quicker and is easier to get to the right consistency.
When you go out fishing take the oil cake container and the powdered spices with you. Mix at the waterside until the required aroma level is reached. Form into balls the size of a cricket ball and throw them into the water trying to keep the balls as concentrated as possible. Fish around that spot, but the closer the better. You can put the oil cake paste on the feeder.
The fish will eat the stuff and the paste makes a good aromatic bait in itself. To stop this you can mix an equal quantity of loamy earth with the cake. Which will bulk it out as well. Alternatively if you cannot be doing with the oil cake then get some rice or wheat bran. Wet it slightly, mix in the spice powder, add the quantity of loam you wish to, ball up and chuck the lot in. The bran will not feed the fish enough but will keep them occupied, there will be a lot of scent to attract the fish and your bait will stand out.
You mentioned competitive fishing so I doubt if you will be allowed to prebait the night before. However if you soak mustard oil cake with water overnight it stinks like the worst French cheese in the morning. Best done well downwind of any human habitation. Chuck this in into your favoured spot the night before. Next morning lay a bed of the sweet spice scented oil cake over this and go to fishing.
You can add anything to the oil cake - ground peanuts, any of a myriad of other sweet scented spices or whatever takes your fancy.
Sounds like a lot of hassle but you can make up a substantial quantity and it lasts for months with the sugar syrup acting as a preservative.
Best of luck
All the best
Lakhyaman.
