Starter: everything but volume
I'm making a second attempt at starting a sourdough culture/starter (the first was a white (unbleached) flour only 100% hydration starter which bubbled nicely, smelt suitably sour but never showed signs of being active enough to increase 'volume' or work in bread fermentation).
This time I started out much as before with a white flour 100% mixture only to switch to an 'organic' wholegrain rye + (same as before) white flour mixture about 3 days in due to lack of activity.
Unfortunately I'm still having the same problem as with my first starter. There's definitely life. It's certainly sour and there are bubbles but there is absolutely no volume. The starter turns to gloop long before any increase in volume can occur.
I've tried different spots in the house (warmer, cooler), tried different ratios of rye to white, tried adjusting 'starter to food' ratio - nothing is improving. It's currently being fed with 50 g rye, 150 g white, 200g (still spring) water and 50g starter at approximately 12 hour intervals (or whenever it looks bubbly and consistency is heading towards liquid).
My thoughts at this point are that I have a culture dominated by acid producing bacteria and not enough yeast. The acid or whatever by-products are turning the mixture into goo and destroying gluten long before yeast has a chance to release enough carbon dioxide. In fact I'm wondering if there's any yeast in there at all. What should I do? This is the second time I've tried to cultivate. Should I give up on this culture? Should I continue feeding it, using it only as 'flavouring' with instant yeast as leavening in any bread I make? Or is there something I'm missing...some secret ingredient?