There are plenty of threads here detailing advice on increasing semen volume - from commercial products, supplements, general hydration and eating certain foods. Thought I'd share my practical experience.
The zinc/l-argenine definetely does work.I bought mass-market supplements from a multi-national health food chain, and took them in the stated doses. The problem is that it is very difficult to perform a scientific experiment. Hydration levels and abstinence levels vary all the time - but I would say that there is a noticeable increase in the amount of semen produced after a few days of taking zinc / l-argenine. The problem is that it is very difficult to quantify it. I didn't go so far as to cum into teaspoons, and the majority of the ejaculations went inside never to be seen again. But those that I did witness were larger - how much is another issue. Commercial products like Semenax claim up to 700%, which I find difficult to believe in isolation. I would say that the zinc / l-argenine gave a 50-100% increase on the first ejaculation only. Given at least 5 hours in between, ejaculations were about 50-100% increased on what I would have expected normally.
The downsides - well I stopped taking the supplements after a month. The increased quantity certainly made me feel good about myself, and it was the first time I'd ever managed to take supplements of any kind consistently. However, after a fortnight, I suffered considerable stomach aches and diarreah, which have not gone away. After another week, I started to experience joint pain in various small joints - fingers, feet etc. This is a continuous pain, and although I can't with any medical certainty put it down to the zinc - I'm willing to bet that I'll recover in fairly short order after giving up. Walking on one of my feet was painful for a couple of days, and currently my fingers have a dull pain in the ligaments during writing or typing.
It's nice to be able to have large loads - but I can tell you first hand- it isn't worth the downside. I can't recommend it.
On a seperate issue, I did try a two-week total abstinence (without zinc), and the volume produced was far greater than the zinc-assisted.