Hello
I have a standard Dachshund who is just over a year and a half.  He currently weighs 10.1 kg and he is very thin.
As a puppy he was on Acana Puppy and now I have been feeding him a choice of Acana Pacifica or Acana Chicken & Potato.  He has 160 grams a day.
However he is very long and lean and I have been told that he should put more weight on.
The thing is if I increase his food even by a small amount he gets soft or runny stools. 
Also I know that stools are supposed to be firm but his are never like this.  Or he may do one firm and the rest are runny and I can't pick them up.
So I am wondering if I should take him off Acana and try something else.  I wanted to give him this food as it has such healthy ingredients but I am not certain it suits my dog.
Please I would be so grateful for some recommendations and wonder if anyone else has had the same issues when feeding Acana to their dogs?
Thank you.

How many times a day is he being fed?  He may tolerate more food if it is split over more feeds.

Twice a day 80g am and 80g pm

And it seems like such a small amount I feel like he must still be hungry after but he doesn't ask for more

Could you up it to 3 times per day until you get some weight on him, his stomach may tolerate it better that way rather than feeding a larger amount over two feeds?

I suppose I could try do you mean 3 lots of 80 grams?

I'm not familiar with your breed or the type of food so wouldn't want to advise on specific amounts however if you know the dog can manage 80g you could try that 3 times a day or could give 3 smaller meals totalling more that the 160g you are currently feeding.

All my dachshunds are raw fed and I don't have any problems with weight

How much and what would you raw feed? I am not familiar with this :-)

Raw green tripe is best for putting on weight plus minced lamb and beef. sardines in oil once a week.  All this can be bought from any pet shop with a frozen section.  As to how much, I never weigh it.  I just picture how big the stomach is and aim to fill that space two or three times a day, depending on the build and age of the dog.  I use Royal Canin as a biscuit, not as a complete, and use just a sprinkle on top of the meat. The raw makes up 95% of the meal.  I also give raw egg as a treat a couple of times a week, raw bones and when I'm preparing our veg, always chop up a little for them.  Start off with a little, don't change the diet too quickly

Raw green tripe is a good idea for putting weight on, it does not cause upset tummies and it is full of good bacteria and enzymes.
I would not suggest that you start using Royal Canin as your dog is not used to this product and the grain that is in it, but use your Acana as a biscuit and sprinkle over any raw meat or tripe.

Sorry 'Wait Ok' just pressed the 'notify button by mistake!!  Agreed, use what you are used to

Although I would recommend  raw I wouldn't advise you doing that without research to get it right.its nit hard and fro a small dog the completes wpuld possible be best. If u have Facebook join on of the raw groups. Something like barf uk or raw feeding UK there are others that are good to.or have a look at anne ridyards website the dogs dinner . If you want another reasonable kibble look at Eden or millies wolfheart neither  have grain or lots of fillers

I have GSP and had same problem with these five star foods. Feed to tolerance of gut - too thin but feed greater amounts diarrhoea
Reverted to using a three to four star food with increased carbs from potato or rice and we were back back to fit but nicely covered
So my take ... Quality rating are all well and good but when they don't suit they aren't that great after all.

If you are thinking about the raw route and want to try it before having to make decisions on meat/offal/veg ratios try a raw complete food like Nutriment or Natural Instinct. More expensive than making your own, but requires less freezer space and you can just weigh out each meal according the the recomendation. DIY raw takes a lot of research to get right, you could go backwards before going forwards! But a complete version is a good stepping stone to see if it's what your dog may like :)

Very interesting thank you all lots to think about.
What 3/4 star dog food did you switch to KLB?

Raw completes:  be careful not all are what they seem. When raw feeders talk about complete they mean the diet must contain  must contain offal bone and meat , fruit and veg is optional.Not all makes contain the first 3 also some are high in bone % than the start recommendation of 10 % that is until you what your dog needs. Make sure you read the packet and not assume because they say it complete that it is. Big bone of contention that isnt regulated
For the first few weeks ( 3-4) its fine not including offal but after that you need to include it. With an adult dog its best to add one protein at atime. ie start wiuth chicken for  a week or two and then add the next

I use autarky salmon and rice or working hpr salmon and potato / duck and potato