Is he right about which? He made 2 statements:
1) you are using a lot of electricity
2) the canister filter added $10/month to the electric bill
As to #2. Don't see which canister you are using. I've found ones that range in wattage from 13 to 51 watts. At 50 watts running 24/7, assuming your home is in tier 2 (it probably is given all the aquariums), the rate is ~$.25/k WH, that works out to $9/month. Pretty darn close.
As to #1. Was posted, but look at what Woodshop posted for 1 tank with no heater. Cost was $3.35/month. Note what JK47 said: "The most wattage used in tanks is from heaters by a landslide." Take $3.35, assume that is 1/5th of the cost when using a heater, then multiply times 4. That's $67. Now adjust for the higher rate in tier 2 versus tier 1 electric rates, and you are over $100/month.
Without knowing the wattage on all the equipment or the tier / electric rates being charged, it's really difficult to nail it down with any accuracy. However, the math is in my earlier post, so if anyone wants to correct that and re-calculate the kWHR and provide a new electric rate, that would be swell.
Just for those who want to do this: California's residential electric rates (at least for PG&E, which covers a huge chunk of the state) is tiered with base rates applied only to 'average' households. An average is at around 550 kWHR per month and moves according to season. Other states may have flat rates across a wide spectrum, or lower base rates. The incremental cost of adding aquariums is not the base rate at the lowest tier unless you run a house with virtually no electricity. It's almost always going to push anyone except a single person in an apartment into tier 2. Those rates are double to triple what base rates are in most other states.