ah wa!

Hahaha.........one thing I disagree........ sentence no. 23 should be removed!

In my opinion, slacking in doing maintenance is not an excuse for a chiller or whatever to went up in flame. By the way, how many people actually clean/maintain their chiller/air-con/refrigerator religiously every few months. Should we say that they are fortunate that their equipment do not catch fire? Personally, I would only buy a chiller from a reputable/established brand. Not just for chiller, it applies to all mission critical equipments.

I think he is refering to O-rings, not gaskets.

Are you refering to those drill bit mean for drilling holes in wood? A hole saw give consistently good results for drilling large holes. Yes, most "one" piece hole saws have a limit to the depth that can be drilled. I use those that have a seperate saw blade and arbor (two pieces type). Those are usually much deeper and are sufficient for most purposes. Use a LOW rpm for drilling pvc and add water or stop occasionally if needed.

Yes, it is widely used in hospital for intravenous drip, dialysis, extraction of platelet from donors etc....

Use a hole saw.

Price revised to $250.

It is a 12VDC low rpm metal geared motor that I've bought from Farnell components.

Yah, no observable ill effect from both tanks. The sensing AC voltage is so weak that I think you have more to worry about stray voltage from your pumps, filter etc...

UPSs are maninly designed to let users have the chance to save their work and do a proper shut down of their computers. Large units that have enough juice for your pump for long period are available but very expensive. I have a small unit and it last less than two hours running a pump. Pretty useless i would say. What I have done is to use two return pumps at all time. The two pumps are powered from two seperate mains( one from the air shelter and the other from the living room). When one of the circuit trip, the other will not be affected because they are powered from different sources. The main pump is also wired to a relay that turns on a battary operated air pump in case of blackout.

For water changes, yes, I would be worried. But for water top up. This tank has a vol of 1000L. The top up water will be like 0.01% or less of the total vol, the chlorine will be so diluted that it dosen't cause any effect. Strong circulations in the tank will dispel the chlorine so that it won't accumulate to a dangerous level. At least, this is what I've observed. Anyway, I will be DIYing a kalkwasser reactor and adding it to the top up system when I have the time.

Ok, low voltage DC are converted into low voltage AC. Because of the vey high sensitivity of the circuit, only a very very low power sensing current is send to the probes. As it is an AC current, all electrolytic chemical reactions at the probes will be nullify. I'm still using this type of system on two tanks. One have been running for 5yrs with the sensors and the other have been running for 2.5yrs. Both of the tanks have done well during these period and no abnormal behaviour is observed. It is so reliable that one of the tanks is plumbed directly to the tap. No false activation, no flood etc.

Is your tank placed in an air-conditioned room? When wind from the fans blow at the water surface. Water at the surface absorb the latent heat energy and evaporate causing a cooling effect. Tank temperature will drop to a lower level than the ambient temperature. When the fans continue to blow, forced convection will take place and the surrounding air( higher temp) will transfer some of the heat energy back to the tank water. What I'm trying to say is that an equilibrium state will set in and the temperature will stabilised even if you add more fans. From the experiments that I've done. A drop of 3-4deg from ambient temperature using fans is about the max(depending on other parameters like ratio of surface area to volume, wave action at the surface etc). I wouldn't waste energy running six fans at the same time. I will shut them down one by one until the point where the temp start increasing then turn on one more fan than at the point.

Yah, I agree that there are many things to consider when building this. It may looks simple but only when you start to think seriously or start to do then will you realised that it is not so easy. The worst part is that unlike a kalkwasser reactor or a protein skimmer which one can obtain the building plans from the internet easily. I've searched the net for days but couldn't find any plans or guides telling you how to do it. In the end, I've to designed it based on my understanding of the basic working principle. The first part is getting a geared motor of low rpm and with sufficient torque to drive the pump head. Finding a suitable bearing is also a problem. At first I bought those wheels used in sliding windows. Knowing that the wheel diameter has to be small so that it will exert sufficient pressure on the tubing to create an air tight condition, I bought the smallest wheels available but it was still too big. I tried to search for suitable bearing but could only find those that are oversized. Companies that have suitable ones like those used in harddisk drive...etc only due with large order and wouldn't entertain non commerical customer. I'm forced to KIV the project until a few months ago when I have more free time. I started to dismantle all the spoilt DVD player, VHS player etc lying around in search for suitable bearing. At last I found it!!! It has a small diameter and is very smooth, I think the roller is made of teflon!!!! It was almost a god's gift for this project! After weeks of searching, brain storming, sawing, filing and soldering etc. I've finally managed to complete it! I'm sorry but I do not have pics of the various stages of construction. The whole place is so messy that I didn't bother to take pic. As for the tubing. I've considered most of the materials that are commonly used for peristaltic pumps like tygon, santoprene, viton, pvc and silicon etc......Different materials have different characteristic which made them suitable for certain demanding environments/fluids. I went to shops specialising in industrial tubings to have a feel of the different tubing. When price, flexibility, resistance to salt water, lifespan etc are all taken into consideration. I decided to use silicon. The silicon tubing is different from those aquarium type, it is tougher and more expensive. Actually, the tubing is not suppose to slide over the bearing, the bearings are suppose to roll over the tubing therefore causing minimal frictional forces. If the tubing are rubbing against the bearing because the bearing is jammed, the tubing will be damaged within a very short time. Feel free to let me know if you're diying it and have any question. I'll try to help if I can.

Hahaha. I've spent so much time sourcing for suitable materials and building it. Especially the bearings. That I think it will be better for you to buy it from commercial sources. I still save some money compared to commerial units with adjustable flow rate but add in the time I spend and it will be a different story. For me, it is the DIY metality and not the cost saving that drive me to built it. I've chosen silicon tubing because it is relatively cheap(compared to other specialised materials) , good enough for reef applications and last longer.