Mixed road gravel a little bigger than pea gravel is best.
8 - 32 mm is optimum
See this thread.http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=199269&page=1
Role of Male Parental Care in Survival of
MARK B. BAIN AND LOUIS A. HELFRICH
Department of Fisheries and Wildlife Science•
Virginia Polytechinc Institute and State U niversity
Blacksburg, Virginia 24061
Mortality of larval bluegills Lepomis macrochirus from predation was measured in 56 nests
guarded by males and 21 nests from which the male guard was removed. Mortality was s ignificantly greater in unguarded nests(median= 68%)than in guardian nests (median= 14%).Fish
traps placed in unguarded nests captured significantly more predators than traps placed in
guarded nests. Bluegills( 3-12 cm total length)w ere the most abundant nest predators Pumpkinseed Lepomis gibbosus (7• -11 cm),largemouth bass M icropterus salmoides(4- 5 cm),and whitefin
shiners Notropis niveus(5 -6 cm) also were nest predators. Nest preparation by male bluegills
exposed coarse gravel( 8-32 mm diameter)and pebbles(3 2-64 mm) in nest substrate and removed particles smaller than 2 mm. Particles larger than 8 mm provided suitable interstitial
space to accommodate bluegill larvae. Survival of larvae was directly correlated with the proportion
of coarse substrate in the nest.
Some points of interest:
Our data from
Virginia implicated juvenile bluegills as the major
predators on bluegill larvae, followed in importance
by pumpkinseed. Dominey (1981)
drew the same conclusions from a New York....
In addition to direct protection afforded larval
bluegills by nest-guarding males, nest preparation
by the male parent influenced survival
of larvae in Lake Caroline. The availability of
suitable nesting substrate has been recognized
as a major factor affecting reproductive success
of centrarchid fishes (Breder 1936; Kramer and
Smith 1962; Muncy et al. 1979).
In laboratory observationss,
coarse particles provided suitable interstitial
space to accommodate yolk-sac bluegill larvae.
That coarse substrate may function as protective
shelter for larvae was supported by field
other factors undoubtedly influence
mortality of tested larvae, our data suggest that
predation, particularly intraspecific predation
(cannibalism), can be a major cause of early
Last pic shows rock size.