# DIY Hydrometer



## jrdeitner

NOTE: this is for a simple hydrometer that is not 100% accurate, and may be up to between .01 and .02 sg off.


yesterday i bought salt and sand for my new tank, but there is one thing i forgot to buy. a hydrometer. i looked online for a diy model and found one on E-how, so i made some adjustments using materials that most aquarists have on hand. as stated above this is not completely accurate, and ideally should only be used for a backup. but, a good idea to know how to make one just in case.

materials needed
- a straw
- some tiny gravel pieces
- some aquarium silicone sealant
- some sewing pins (optional)


first cut the straw to make approx. a 2 1/2 inch piece. then put a few small gravel pieces inside the straw to weigh it down. then put a blob of sealant down on the bottom to make it watertight ( if its not watertight it wont work). thats all for the making of it, but now you have to calibrate it with liquids of known density. of course plain distilled ( not tap) water has a specific gravity of 1, at the bottom of this post i will include a chart with the specific gravity of many other liquids to calibrate it with. to calibrate it, put the hydrometer in the liquid and mark where it meets the water. on mine i use pins, but then you have to compensate for the weight of the pins. i only have three pins in mine, one for 1 sg, one for 1.025 and one for 1.060. of course you have to look very close to find the slightest difference, but it works. and thats it! a simple hydrometer you can make in minutes. i will include attachments with pictures of mine, the second picture will be regular distilled water- you can see the top pin is half in half out.
in the third and fourth it is in saltwater and you can see the middle pin is right around the water level. so yeah i hope this helped and its simple enough its something every SW aquarist should know how to do, just in case.
if you have any questions, just ask.





thanks to SIMetric.co.uk for the chart

1,1,2-Trichlorotrifluoroethane 25 C 1564.00 
1,2,4-Trichlorobenzene 20 C 1454.00 
1,4-Dioxane 20 C 1033.60 
2-Methoxyethanol 20 C 964.60 
Acetic Acid 25 C 1049.10 
Acetone 25 C 784.58 
Acetonitrile 20 C 782.20 
Alcohol, ethyl 25 C 785.06 
Alcohol, methyl 25 C 786.51 
Alcohol, propyl 25 C 799.96 
Ammonia (aqua) 25 C 823.35 
Analine 25 C 1018.93 
Automobile oils 15 C 880 - 940 
Beer (varies) 10 C 1010 
Benzene 25 C 873.81 
Benzil 25 C 1079.64 
Brine 15 C 1230 
Bromine 25 C 3120.40 
Butyric Acid 20 C 959 
Butane 25 C 599.09 
n-Butyl Acetate 20 C 879.60 
n-Butyl Alcohol 20 C 809.70 
n-Butyl Chloride 20 C 886.20 
Caproic acid 25 C 921.06 
Carbolic acid 15 C 956.30 
Carbon disulfide 25 C 1260.97 
Carbon tetrachloride 25 C 1584.39 
Carene 25 C 856.99 
Castor oil 25 C 956.14 
Chloride 25 C 1559.88 
Chlorobenzene 20 C 1105.80 
Chloroform 20 C 1489.20 
Chloroform 25 C 1464.73 
Citric acid 25 C 1659.51 
Coconut oil 15 C 924.27 
Cotton seed oil 15 C 925.87 
Cresol 25 C 1023.58 
Creosote 15 C 1066.83 
Crude oil, 48° API 60 F 790 
Crude oil, 40° API 60 F 825 
Crude oil, 35.6° API 60 F 847 
Crude oil, 32.6° API 60 F 862 
Crude oil, California 60 F 915 
Crude oil, Mexican 60 F 973 
Crude oil, Texas 60 F 873 
Cumene 25 C 860.19 
Cyclohexane 20 C 778.50 
Cyclopentane 20 C 745.40 
Decane 25 C 726.28 
Diesel fuel oil 20 to 60 15 C 820 - 950 
Diethyl ether 20 C 714 
o-Dichlorobenzene 20 C 1305.80 
Dichloromethane 20 C 1326.00 
Diethylene glycol 15 C 1120 
Dichloromethane 20 C 1326.00 
Dimethyl Acetamide 20 C 941.50 
N,N-Dimethylformamide 20 C 948.70 
Dimethyl Sulfoxide 20 C 1100.40 
Dodecane 25 C 754.63 
Ethane -89 C 570.26 
Ether 25 C 72.72 
Ethylamine 16 C 680.78 
Ethyl Acetate 20 C 900.60 
Ethyl Alcohol 20 C 789.20 
Ethyl Ether 20 C 713.30 
Ethylene Dichloride 20 C 1253.00 
Ethylene glycol 25 C 1096.78 
Fluorine refrigerant R-12 25 C 1310.95 
Formaldehyde 45 C 812.14 
Formic acid 10% concentration 20 C 1025 
Formic acid 80% concentration 20 C 1221 
Freon - 11 21 C 1490 
Freon - 21 21 C 1370 
Fuel oil 60 F 890.13 
Furan 25 C 1416.03 
Furforol 25 C 1154.93 
Gasoline, natural 60 F 711.22 
Gasoline, Vehicle 60 F 737.22 
Gas oils 60 F 890 
Glucose 60 F 1350 - 1440 
Glycerin 25 C 1259.37 
Glyme 20 C 869.10 
Glycerol 25 C 1126.10 
Heptane 25 C 679.50 
Hexane 25 C 654.83 
Hexanol 25 C 810.53 
Hexene 25 C 671.17 
Hydrazine 25 C 794.52 
Iodine 25 C 4927.28 
Ionene 25 C 932.27 
Isobutyl Alcohol 20 C 801.60 
Iso-Octane 20 C 691.90 
Isopropyl Alcohol 20 C 785.40 
Isopropyl Myristate 20 C 853.20 
Kerosene 60 F 817.15 
Linolenic Acid 25 C 898.64 
Linseed oil 25 C 929.07 
Methane -164 C 464.54 
Methanol 20 C 791.30 
Methyl Isoamyl Ketone 20 C 888.00 
Methyl Isobutyl Ketone 20 C 800.80 
Methyl n-Propyl Ketone 20 C 808.20 
Methyl t-Butyl Ether 20 C 740.50 
N-Methylpyrrolidone 20 C 1030.40 
Methyl Ethyl Ketone (MEK) 20 C 804.90 
MEK 25 C 802.52 
Milk 15 C 1020 - 1050 
Naphtha 15 C 664.77 
Naphtha, wood 25 C 959.51 
Napthalene 25 C 820.15 
Ocimene 25 C 797.72 
Octane 15 C 917.86 
Olive oil 20 C 800 - 920 
Oxygen (liquid) -183 C 1140 
Palmitic Acid 25 C 850.58 
Pentane 20 C 626.20 
Pentane 25 C 624.82 
Petroleum Ether 20 C 640.00 
Petrol, natural 60 F 711.22 
Petrol, Vehicle 60 F 737.22 
Phenol 25 C 1072.28 
Phosgene 0 C 1377.59 
Phytadiene 25 C 823.35 
Pinene 25 C 856.99 
Propane -40 C 583.07 
Propane, R-290 25 C 493.53 
Propanol 25 C 804.13 
Propylene Carbonate 20 C 1200.60 
Propylene 25 C 514.35 
n-Propyl Alcohol 20 C 803.70 
Propylene glycol 25 C 965.27 
Pyridine 25 C 978.73 
Pyrrole 25 C 965.91 
Rape seed oil 20 C 920 
Resorcinol 25 C 1268.66 
Rosin oil 15 C 980 
Sabiname 25 C 812.14 
Sea water 25 C 1025.18 
Silane 25 C 717.63 
Sodium Hydroxide (caustic soda) 15 C 1250 
Sorbaldehyde 25 C 895.43 
Soya bean oil 15 C 924 - 928 
Stearic Acid 25 C 890.63 
Sulphuric Acid 95% conc. 20 C 1839 
Sugar solution 68 brix 15 C 1338 
Sunflower oil 20 C 920 
Styrene 25 C 903.44 
Terpinene 25 C 847.38 
Tetrahydrofuran 20 C 888.00 
Toluene 20 C 866.90 
Toluene 25 C 862.27 
Triethylamine 20 C 727.60 
Trifluoroacetic Acid 20 C 1489.00 
Turpentine 25 C 868.20 
Water, pure (more temperatures) 4 C 1000.00 
Water, sea 77 F 1021.98 
Whale oil  15 C 925 
o-Xylene 20 C 880.20


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