Maintaining Tension in a Single Speed Chain

[BannanaMan]

Recently I took the bike into the workshop because the Shimano Nexus hub was playing up. Whilst they had it in the mechanic put a new chain on. Unfortunately the chain includes all the links that I paid for consequently the new chain is worse than the old one was.
If I had done it myself I would have bought a single half-link and used that to substitute for one of the links.
The mechanic seemed to suggest that I should consider a device which looks like a derailleur arm or to use a complete half-link chain.
Another option is to change the ratio of Chainring to Sprocket to negate the problem.

Is there anything wrong with using a single half-link in the chain?

 

[FrankCrank]

Your description is not exactly clear, but to answer the last question, half-links are fine for this application.

 

[lenfield]

Why not try taking links out of the existing chain? If you can't get the tension exactly right you can buy a single half link for it. It would be cheaper than buying a whole new chain.