I regularly get a lot of spam comments on my unpopular blog, and it's really annoying. Of course the comments will not show up on the blog without my approval, and there is no way I will approve such comments. How to make your blog not interesting to spammers?

I think it is just something common, I have seen it over tons of blogs, it's just something you need to ignore.

Add captcha? These are some bots probably, just trying to spam random blogs.

Good idea, but that can put off general users from posting comments.

so either put up with the spambots or add captcha or some other measure that will only allow humans to register and add articles

I believe so, as it happened to my other blogs as well. I hate it that I have to regularly visit the comment page and delete the spam comments.

I have a few Boonex Dolphin sites and used to get the same spambot comments even with Captcha, then on the boonex forums i found a solution to add a 'what is' question in the registration form that needs answered by a human and since adding this i have had no spambot comments added.

Technically speaking, the only way to make your blogs uninteresting for spammers is to a) downgrade their Google PR or delist them from Search engines; b) depreciate their content; c) close them.

Spammers will keep trying to break-in if you have well-recognized, popular blogs. You can always close comments, but you'd loose the regular readers and posters.

If you are making money out of these blogs, try to migrate them into any CMS which makes for spammers harder to register and post. If you run your own (or just not very popular) CMS, the automated scripts some folks use will not work.

thats why we decided to use Dolphin, also its more than just a standard blog (http://demo.boonex.com/)

Why would you not want to make your blog appealing to spammers? Spammers are (ideally) looking for the most popular blogs with the highest pagerank. The more popular your blog comes the more spammers you will attract. Typically installing and using akismet handles most of the spam so it shouldnt be an issue.

Something that I have noticed from running my own site. The easier the site is to find the more spam you get. I remember when I was getting lots of spam on my site. I set up captcha, added a mod made by stop forum spam and still I was getting lots of spam. I was even banning every ip that spammers used. I had so many ips banned that you could not pull up the banned ip list with out crashing the browser. I think it had over 2000 entries. I eventually just updated the forum software which included a new spam protection.
I was still getting spam but I was also using vps and trying to configure a firewall. I then came across incapsula.com and it reduced the spam by more then 75%. Even after I went back to shared the spam has not been as bad as it was. However I still get spam so I am thinking about going back to using incapsula but I had a few questions about it before I do. Any way that is another topic.

most spam will be from spambots, so this what most protection is geared upto fight

I have 2 dolphin sites that are not busy sites, but was bombarded by spambots, even with captcha added. when i updated dolphin i was searching the developer forum and come across a way to add a human check box, that needed a human to check and give a written answer. this has cut down the spam by 90% and others that i get you can tell are spam and they give strange names and emails, but USA states that are in other countries. I have one that listed Texas in France

That is funny. My forum has a human verification like that. You can make up the questions and have as many questions as you like. You can even make required answers. If they do not answer correctly they are not able to register. This is part of the spam protection that was built into the latest forum software. It does help that is for sure. No more hundreds to thousands of spam again. It is down to a handful now.

Disable comments

This is just one of those things that you know are going to happen. We have editor approved comments only so no ones comments get through without us giving them a look over first. Other then this blogs are just like forums and people with spam them with bots. Captcha or what is questions like others have said help prevent or limit them if you do not wish to have your blog approved only.