Is it really worth boosting hook baits by dosing them with glugs or flavours?
Glugs and flavours may sound like a great way to attract carp to a hookbait but in some cases it could end up as overkill. A carp's taste receptors are a lot more complex and sensitive than ours. If something taste/smells strong to us, then it will be positvely overpowering to them! It may well attract a carp over towards your area but then it may repell them when up close to it. Most shelflife boilies are generally over-flavoured already in order to attract the carp to them so I would be cautious about adding it too much. Rather, think about using an amino acid based products to attract carp. products such as corn steep liquour, belachan, fish oil, betaine and green-lipped mussel are excellent at attracting fish into a swim and stimulate feeding. these will more likely complement a shelflife boilie rather than overpower it will flavour. If you need any more convincing on wether to waste money then think about the plastic imitation baits. Many carp have been caught using these and they have no smell!!
Do highly visible baits produce better catch results?
It really depends on the water, as well as many other factors. I like to use high-viz baits on coloured waters because I feel it helps a carp zoom in on my hook bait. For the same reason, I always use high-viz boilies when fishing in weed. I have found on clear lakes some of the wary carp will ignore them. It may depend on how much angling pressure is on the lake although, I think they are worth a try on one rod in order to assess their effectiveness.
What groundbait or particles are best to use on a hard water?
It can be anything to be honest. Depends on the make up of the hard water in question, I suppose. To answer this question, let's make a few assumptions. I would guess that quite a few hard waters contain lots of natural food sources. The reason why carp do not have to rely on anglers bait and hence why they are hard to catch. I would also guess that most natural food sources are relatively small items and have a natural scent to them. Bearing this in mind, I would try hempseed. It is a small, has a natural food smell to it and its highly visible in large patches due to the black/white colour. The combination of benefits is a close match to the natural sources in the lake, and therefore carp may not be too suspicious of it in large quantities. Hemp can also help to hold carp in an area for hours as they all just love it! If you feel that large beds of hempseed may spoke away carp, then try it in PVA bag. What? You think it will melt the bag? Simply smother icing sugar over it and the PVA bag will not melt!
Can you recommend any cheap, productive boilies that catch big carp?
Straight answer - NO!
For carp angling, cheap often means poor quality catch rates. The only way to use cheap baits and still catch plenty of carp is if you're lucky enough to be fishing a lake that is so full of carp with hardly any natural food sources. The fish would be so hungry that they would try to eat the end tackle! You need a good quality bait on the hook if you want to catch some of the bigger, target carp. Think of when you're selecting a meal. Do you choose a tasty, nutritious meal or do you grab a bland, over-flavoured, uninspiring snack?
Why are there so many flavours and additives in carp bait, surely carp do not have sophisticated senses like humans?
After being caught, some carp will learn to associate danger with a particular flavour or scent. As an angler, you have no way of knowing exactly which carp have been caught on which flavours in the past, so we need plenty of choice to attempt them to another attractant. For this reason, I believe it's good practice to try out various flavours on a particular water. Maybe use a different bait on each rod, especially on a new lake. I often try to use a unique bait, such as a flavour combination which other angler's are not using it. Obviously, if you know the local lads and they're telling you what bait is working, then always stick with this at least on one rod!