Hallo, mayby it will help the use of some plastics to copy the surface on, and then use current methods to isolate fungi, printing the sample on an agar media, or a particular part of plastics would be possible to cut off and cultivate. Some kind of sterilization the surface of plastic, in vapors of e.g. formaldehyd. May be the spatial distribution of species may be recognized, active mycelia or spores... Which microniche... Even more, the plastic may be filled by some selective media... Good game!

Look at this article - accessible through Researchgate http://www.researchgate.net/publication/230577503_Fungi_Their_role_in_deterioration_of_cultural_heritage/file/d912f5018fa4d2cbfd.pdf

Please be aware that fungi responsible for deterioration of cultural properties are often osmophilic and grow very slowly.  You'll need to discern these from the general fungal presence - most of which will be incidental.  What media do you plan to use and can you supplement your work with someDNA analysis?

Article Fungi: Their Role in Deterioration of Cultural Heritage

I suggest you to wash rocks surface with small quantity of water , then collect water and repeat washing with collected water five times and collect water,prepare liquid eligible medium and add 2 ml  of collected water to 30 ml of liquid medium and incubate for 10 days . Then transfer one ml on the surface of solid media and incubate  for few days

Thank you for your help/ideas, they come in handy. For now i'm using "the Koch metod" (cotton swab), adhesive plastics (duct tape) and small pieces of media onto the substrate.

Now for the isolation I'm thinking Dichlorane-Rose Bengal Media (but i do not have any) so I'll try some water- agar media with Chloramphenicol (MEA - not so great results).  If u have any ideas/ recommendations, even questions do not hezitate to contact me. All the best!