You can use this SQL to monitor table size and #rows by schema.

SELECT substr(OWNER||'.'||TABLE_NAME,1,35) "Table",
ceil(decode (blocks,0,initial_extent*min_extents/(1024*1024),
null,initial_extent*min_extents/(1024*1024),
(initial_extent*min_extents + ((blocks*4096) - (initial_extent*min_extents)))
/(1024*1024))) "Size (MB)" , NUM_ROWS
FROM DBA_TABLES
WHERE OWNER in ('')
and ceil(decode (blocks,0,initial_extent*min_extents/(1024*1024),
null,initial_extent*min_extents/(1024*1024),
(initial_extent*min_extents + ((blocks*4096) - (initial_extent*min_extents)))
/(1024*1024))) <= 4
ORDER BY 2 desc

Replace with actual schema name and blocks*4096 with your db_block_size.

Regards.