Join Date: Feb 2020
Location: Blacksburg, VA, USA
I know this is an old thread, but I currently have both of these installed and can state some differences and similarities. I am running each on its own Marineland C-220 canister filter. I put a 5/8" to 1/2" barbed adapter on each side of the ISTA to put it inline with my 5/8" tubing.
Similarities: These definitely work on the same principal, are extremely similar design and are made of the same type of plastic. The inside of the upper "impeller" (the slotted one) is rough. I sanded mine to make it run smoother. Air bubbles will cause more noise and the "impellers" to slow and/or stop.
Differences: The ISTA is blackish and the Sera is brownish. The ISTA takes 12 mm ID hose, which is slightly small for 1/2" hose, although it does work, it can be a little loose. The Sera takes 5/8" ID hose very well. Standard CO2 line fits the ISTA better than it does the Sera.
I observed something on the Sera which I fixed before I installed the ISTA: decreased outflow will cause the impellers to slow and/or stop. I had a DIY inline heater which was stepped down to 1/2" hose on the Sera. The impellers stopped. I increased the size of the heater barb and the impellers have been running fine ever since. I have not observed this on the ISTA, but I can only imagine that the same holds true.