How to pick a water pump for automatic water change system?

[Smertrios]

If designing a fish room that is going to make use of water from a tank and pressure compensating drop irrigation emitters for water changes how do I determine the number of emitters a single pump can supply water to at once?

For example the following water pump is $40 and pumps 1 gallon per minute "float" then another number saying 3.2 liters per minute *but* how much water can it deliver at over 8 psi to run the emitters?

http://www.ebay.com/itm/Brand-New-RV-12V-Water-Pump-1-0GPM-/150689688411?pt=Motors_RV_Trailer_Camper_Parts_Accessories&vxp=mtr&hash=item2315ce2b5b#ht_2650wt_767

3.2 LPM would be enough to supply water for just over 100 1/2 GPH emitters.

 

[Smertrios]

This seems like a superior RV water pump for $50...
http://www.adventurerv.net/wfco-water-pump-artis-portable-12v-gpm-camper-p-23660.html

Seems so much easier to get a 110v lawn pump and have more than enough than trying to get just enough => A portable Wayne lawn pump would cost less (After adding in the cost of a power supply for an RV pump) and provide more water and at high psi.

soo... problem solved by choosing the right equipment. Just thinking about it right now no plans to do it yet.