The fresh water tanks SKU Icon Direct 12735 and 12736 have fittings installed on one end only, which may protrude slightly beyond the tank body. If you plan to place these tanks end to end, note that the fittings could interfere with a flush connection. For a cleaner installation, consider using a similar tank without pre-installed fittings so you can position fittings as needed. We can also inquire with the manufacturer about custom tanks without fittings. Regarding the WT2472 tank, currently, the standard size maintains a 12" height and 12" width, but longer lengths are not confirmed; we recommend using our Tank Finder tool to explore sizes that fit your space. Lastly, black tanks designed to control algae growth are not indicated as standard options; please contact us if you need assistance sourcing specialized tanks.