Stream mesocosm component design

Mesocosms don't have to be complicated, they can just be lengths of guttering - in the one pictured above, the ends are closed with perspex, but you can use guttering 'ends'.  

You then need two small tanks, one as 'head' filling constantly, and one as a 'sink' emptying constantly with a pump to feed the head-tank.  The guttering needs just one hole with a plumbing threaded join and a small pipe to create a clean flow to the sink-tank.  The head-tank needs a hole with a plumbing threaded join and a small L bend. I would place a pump in the sink with its output pipe leading to the head, on a 'slow' flow rating.

Aeration is provided by the fall of water from the pump tubing entering the head-tank, water exiting the output of the two tanks.

The single module illustrated can be replicated any number of times to study combinations of species, substrate composition, and flow rates simultaneously.

I have used these to study freshwater molluscs such as slipper shells, freshwater clams, and freshwater limpets examining substrate preference (geology) in the stream.

Food supply is provided by algae - and either (or both) of the tanks can be used to culture algae which helps sedimentation of the algae among the substrate in the guttering section. Attention needs to be given to fouling from birds and dust entering the mesocosm if outdoors.

Selected References:

Ellis, A.E. British snails. (1969 reprint) Clarendon Press, Oxford (1926).

Ellis, A. E. British freshwater bivalve Mollusca. Synopses of the British Fauna No. 11, The Linnean Society of London (1978).

Waldén, H. W. A nomenclatural list of the land Mollusca of the British Isles. Journal of Conchology 29 (21-25) (1976).

Robert Hudson, Jerry Farris, Cristi Bishop, Propagation and Culture of Freshwater Mussels, Freshwater Bivalve Ecotoxicology, 10.1201/9781420042856, (65-94), (2006).

MAYUVA AREEKIJSEREE, ARUNEE ENGKAGUL, SATIT KOVITVADHI, UTHAIWAN KOVITVADHI, AMARA THONGPAN, KRISNA RUNGRUANGSAK-TORRISSEN, Development of digestive enzymes and in vitro digestibility of different species of phytoplankton for the culture of early juveniles of the freshwater pearl mussel, Hyriopsis ( Hyriopsis ) bialatus Simpson, 1900, Invertebrate Reproduction & Development, 10.1080/07924259.2006.9652215, 49, 4, (255-262), (2006).

Keller, A.E. & Zam, S.G.  Simplification of in vitro culture techniques for freshwater mussels. Environmental Toxicology and Chemistry 9, 10, (1291-1296), (1990).

Paula Lima, Manuel Lopes Lima, Uthaiwan Kovitvadhi, Satit Kovitvadhi, Christopher Owen, Jorge Machado, A review on the in vitro culture of freshwater mussels (Unionoida), Hydrobiologia, 10.1007/s10750-012-1078-0, 691, 1, (21-33), (2012).

RICARDO CUNHA LIMA, WAGNER E.P. AVELAR, A new additive to the artificial culture medium for freshwater bivalve culture in vitro, Invertebrate Reproduction & Development, 10.1080/07924259.2010.9652320, 54, 2, (89-94), (2010).

Peter J. Jacobson, Donald S. Cherry, Jerry L. Farris, Richard J. Neves, Juvenile freshwater mussel (Bivalvia: Unionidae) responses to acute toxicity testing with copper, Environmental Toxicology and Chemistry, 10.1002/etc.5620120512, 12, 5, (879-883), (2009).