...fish mothers determine offspring size?
Fish mothers can tailor offspring phenotype to the environment in which young will grow up. The habitat mothers experienced as juveniles will allow them to predict their offspring's environment better than the conditions in the adult home range. In this case maternal decisions about investment in offspring quality should already be determined during the juvenile phase of mothers. Testing this hypothesis, it was foud that the females raised in a poor environment produced larger young than females raised without food limitations, irrespective of the feeding conditions experienced during adulthood. The cause was a higher investment in eggs and to faster larval growth. Apparently, mothers prepare their offspring for similar environmental conditions to those they encountered as juveniles. Under natural conditions, juveniles live in a different and much narrower range of habitats than adults.
[Taborsky, B. Mothers determine offspring size in response to own juvenile growth conditions. In Biology Letters, 2006, 2, 225-228] ]

...gastritis in Tropheus is caused by bacteria?
Necrotic and granulomatous gastritis is described in Lake Tanganyika cichlids. Clostridium hastiforme and flagellated protozoa were both associated with the reaction but the significance of either is unknown. Nevertheless, treatment of surviving fish with ampicillin was carried out and mortalities ceased. The possible involvement of an unsuitable diet as a predisposing factor is discussed.
[Ferguson, H.W. et al. Gastritis in Lake Tanganyika cichlids (Tropheus duboisi). In Vet Rec., 1985, 116, 687-689]

...there are the differences in a way of algae grazing between the cichlids in Lake Malawi?
Feeding angle differences among Labeotropheus trewavasae, Labeotropheus fuelleborni, Melanochromis auratus, Petrotilapia spp., Pseudotropheus elongatus, Pseudotropheus tropheops, Pseudotropheus zebra, and Pseudotropheus gracilior were examined. The median feeding angles ranged from 35 degrees to 91 degrees. There are four feeding angle groups among the eight rock-dwelling species that were examined: (1) Labeotropheus trewavasae (35°), (2) Labeotropheus fuelleborni, Melanochromis auratus, and Pseudotropheus elongatus (44-48°), (3) Pseudotropheus tropheops (53°), and (4) Petrotilapia spp., Pseudotropheus gracilior and Pseudotropheus zebra (86-91°). Feeding angles measured in the laboratory were congruent with field data and no significant effect of feeding angle was attributed to the tank chambers. No significant differences in the extent or distribution of food acquisition were observed.
[Hale, E.A. An investigation of the utility of feeding angles among Lake Malawi rock-dwelling cichlids (Teleostei: Cichlidae). Doctoral dissertation, The Pennsylvania State University, 1997]